Gene-Guided Antidepressants?

Over the past couple of years, "Big Pharma" has largely moved away from psychiatric drug development. This shift has been widely discussed.

But another trend has been happening over the same time period - or so it seems to me. This is the rise of small companies who offer techniques for diagnosing mental illness, or predicting which drugs will work best. Generally (it seems) partnerships between venture capitalists and psychiatry (ex-)researchers, these enterprises might be dubbed "Little Pharma".

The latest is a company called AssureRx Health, Inc. According to a paper just published, they offer

a pharmacogenomic algorithm designed to improve the safety and efficacy of prescribing antidepressant and antipsychotic medication... based on the genotyping of both copies of five genes.

From this, you end up with a report giving each drug a rating of green, yellow, or red (see above).

The price is not provided on their website.

According to the paper, they gave 26 depressed patients normal treatment at the discretion of their psychiatrist, while 25 got treatment guided by the AssureRx algorithm. It was non-randomized, and unblinded so there's a clear possibility of a placebo effect.

Anyway, the results were...

For the first 4 weeks of treatment, there was no difference between the two groups whatsoever in terms of depression symptom scores - they both improved. But then by week 8, the unguided patients abruptly got worse, while the AssureRx-guided ones continued to benefit. This is an unusual pattern of improvement in an antidepressant trial.

Previously, I wrote about another Little Pharma antidepressant prediction scheme. It used a  different approach, measuring brain electrical activity using a technique called "rEEG", rather than genetics. But the basic idea is the same... and so are the problems.

As I said last time:

There were two groups and they got entirely different sets of drugs. One group also got rEEG-based treatment personalization. That group did better, but that might have nothing to do with the rEEG: they might have done equally well if they'd just been assigned to [those drugs] by flipping a coin. We cannot tell, from these data, whether rEEG offered any benefits at all.

In the AssureRx paper, we can't even tell whether the two groups got different kinds of drugs, because the meds used aren't reported, but if they did differ then that would offer an alternative explanation for the differences in outcome: maybe the 'guidance' just recommended better drugs overall, with the genes being just a sideshow. Or maybe it's a placebo, as I said.

Moving on, I also wrote... 

What's curious is that it would have been very simple to avoid this issue. Just give everyone rEEG, but shuffle the assignments in the control group, so that everyone was guided by someone else's EEG. So you'd give control Patient 2 the drugs that Patient 1 should have got, and vice versa; swap 3 and 4, 5 and 6, etc.

This would be a genuinely controlled test of the personalization, because both groups would get the same kinds of drugs... and it would allow the trial to be double-blind: in this study the investigators knew which group people were in, because it was obvious from the drug choice...

It is odd that Little Pharma never seem to do such real vs. muddled prediction studies, as they'd be really informative as to whether their approach is a helpful innovation as opposed to an expensive, meaningless red herring. Hmm.

Hall-Flavin, D., Winner, J., Allen, J., Jordan, J., Nesheim, R., Snyder, K., Drews, M., Eisterhold, L., Biernacka, J., and Mrazek, D. (2012). Using a pharmacogenomic algorithm to guide the treatment of depression Translational Psychiatry, 2 (10) DOI: 10.1038/tp.2012.99

Do Antidepressants Make Some People Worse?

Antidepressants may help depression in some people but make it worse for others, according to a new paper.

This is a tough one so bear with me.

Gueorguieva, Mallinckrodt and Krystal re-analysed the data from a number of trials of duloxetine (Cymbalta) vs placebo. Most of the trials also had another antidepressant (an SSRI) as well. And the SSRIs and duloxetine seemed to be indistinguishable so from now on I'll just call it antidepressants vs. placebo as the authors did.

People on placebo got, on average, moderately better over 8 weeks.

People on antidepressants fell into two classes. The largest class got, on average, a lot better. But about 25% did poorly, staying just as depressed as before. This "nonresponder" group did much worse than the placebo group - again on average. Here you can see the mean "trajectories" of depression symptoms (HAMD scores) in the three groups:

This raises the scary possibility that while antidepressants are helping some people, they're harming others. But hang on. It's complicated.

First off, maybe this is all a statistical illusion. When the authors say that the people on drug fell into two classes, what they mean is that when you try to model the data according to a certain mathematical model, assuming either 1, 2, 3 or 4 underlying classes, the 2 class solution was the best fit. While for placebo a 1 class solution was best.

We considered linear, quadratic, and cubic trends over time, with between 1 and 4 trajectory classes. We also considered piecewise models with a change point at 2 weeks, linear change before week 2, and quadratic change after week 2. The selection of the best model was based on the Schwartz-Bayesian information criterion and on the Lo-Mendell-Rubin (LMR) likelihood ratio test...

That's nice... but they don't present the raw data. They don't tell us whether, looking at the individual trajectories of people on antidepressants, you'd actually see two classes. What I want is a graph of how likely people are to get better by a certain amount. If Gueorguieva et al are right, I want it to look like this i.e. bimodal -

We're not shown this graph. I'll eat my hat if it does look like that, frankly, because if it did people would have noticed the bimodality in antidepressant trials ages ago.

True, statistical models can tell us things that aren't obvious by inspection, so even if this isn't what the data look like, they might still be right. It could be that the two "peaks" are so broad, and there's so much random noise, that they blur into one.

However, it's also true that you can fit an infinite number of models to any set of data and at some point you have to step back and say - am I making this more complicated than it needs to be?

It could be that a 2-class model is better than a 1-class model for the people on antidepressants, but only because they're both crap, and really, every patient has a different, unpredictable trajectory which is poorly captured by such models.

Let's assume however that this is true. What would it mean?

Firstly, the fact that one class of people on antidepressants does worse than people on placebo doesn't mean that antidepressants are harming them. The authors miss this point, when they say

there are 2 trajectories for patients treated with antidepressants and 1 trajectory for patients treated with placebo [so] some patients would seem to be more effectively treated with placebo than with a serotonergic antidepressant.

But that's fallacious. It treats a purely statistical entity as representing individual people. Suppose that what antidepressants do is to take people who, on placebo, would have improved a bit, and make them improve a bit more than they otherwise would have. You'd then end up with more people doing well, but also fewer people doing moderately because they'd have been "moved up" out of the middle ground.

That "nudging people off the fence" could lead to a bimodal distribution and two distinct classes. But in this case the people doing badly would have done badly either way. The drug didn't make them do badly, it just made doing-badly into a class. On the other hand it's consistent with antidepressants doing real harm. We can't tell.

We do know that other randomized controlled trials show very convincingly that in a small minority of people, mostly but not exclusively young people, antidepressants do worsen suicidal thoughts and behaviours. So it's plausible. But we just don't know yet.

What worries me is that this paper is the latest in a series of attempts  to use, well, creative statistical approaches to antidepressant trial data. This one is nowhere near as dodgy as the Cherrypicker's Manifesto I discussed last year, but it cites that paper and others by the same group. The first sentence of the Abstract of this paper makes the intention clear:

The high percentage of failed clinical trials in depression may be due to high placebo response rates and the failure of standard statistical approaches to capture heterogeneity in treatment response.

In other words, the reason clinical trials of new antidepressants often fail to show a benefit over placebo is not because the drugs are crap but because the statistics aren't subtle enough. And you can see where this is going: if only we could use statistical models to find the people who do benefit from antidepressants, and compare them to placebo, there'd be no problem...

Gueorguieva R, Mallinckrodt C, and Krystal JH (2011). Trajectories of depression severity in clinical trials of duloxetine: insights into antidepressant and placebo responses. Archives of General Psychiatry, 68 (12), 1227-37 PMID: 22147842

A Psychedelic Tale of Two Neurotransmitters

An unexpected interaction between neurotransmitter systems may explain psychosis and hallucinations, according to a fascinating new paper.

Serotonin (5HT) and glutamate are two neurotransmitters. Up until now, it was thought that they acted independently. A given neuron might have receptors for both serotonin and glutamate, but they didn't interact: serotonin would never affect the glutamate receptors, and vice versa.

The new research overturns that view. Authors Miguel Fribourg and colleagues of Mount Sinai School of Medicine show, in a series of elegant experiments in mice, that different receptors can cluster together, forming a complex. The two receptors, serotonin's 5HT2A and glutamate's mGluR2, can talk to each other.

However, this doesn't seem to happen under normal conditions. Serotonin and glutamate don't seem to trigger the receptor interaction, or at least not very much. Only certain drugs can do it. And this is where it gets really interesting.

Psychedelic drugs, like LSD, have long been thought of as 5HT2A agonists, binding to the receptor and activating it. It turns out that this was only half right. They also inhibit mGluR2 transmission via the receptor complex. Serotonin itself is a 5HT2A agonist, but it doesn't do that. So psychedelics seem to be a kind of (for want of a better word) "superagonist".

It also works in reverse. The antipsychotic drugs clozapine and risperidone are known as 5HT2A antagonists. But Fribourg et al show that they also activate the mGluR2 receptor.

And the cross-talk can go in the other direction. Certain molecules that act on mGluR2 can either inhibit or promote 5HT2A. Unlike psychedelics and antipsychotics, these mGluR2 drugs have not been tested in humans yet. But these data predict that they will have psychedelic-like or antipsychotic-like effects, depending which way they work.

The interaction turns out to be all about G proteins, which are part of the chain of transmitter substances that convey signals within the cell, in response to neurotransmitters outside it. Here's a chart showing the effects of various drugs on the balance between different G proteins: the LSD-like psychedelic DOI has the opposite effect from the antipsychotics clozapine and risperidone.

This paper builds on a previous one from the same team showing that psychedelic 5HT2A "agonists" (like LSD and DOI) have different effects on G proteins from other, non-psychedelic agonists. That was interesting in itself but by adding glutamate to the picture, this new paper is really ground-breaking.

This goes a long way to explaining one of the mysteries of serotonin which is this:  if 5HT2A agonists like LSD are psychedelic, why aren't antidepressants the same? Almost all antidepressants work by increasing extracellular 5HT levels. That ought to mean that they activate 5HT2A receptors (indirectly). This explains why not - 5HT alone doesn't promote the crucial 5HT2A-mGluR2 interaction.

Taken together, these interesting results show clearly that 5HT2A and mGluR2 are hooking up and doing something exciting. Certainly in terms of how hallucinogens work.

I'm less convinced that this can directly explain antipsychotic effects though. The problem is that while newer "atypical" antipsychotics act on 5HT2A, the older antipsychotics don't, and atypicals are at best only slightly more effective on average.

What we don't yet know is whether this kind of complex receptor interactions can happen with other receptors. I'd have thought it unlikely that these two receptors were the only ones that could ever do it. The synapse looks like it's more complex than we could have imagined.

Fribourg M, et al. (2011). Decoding the Signaling of a GPCR Heteromeric Complex Reveals a Unifying Mechanism of Action of Antipsychotic Drugs. Cell, 147 (5), 1011-23 PMID: 22118459

Another Antidepressant Bites The Dust

Yet another up-and-coming antidepressant has flopped.

A paper just out reveals that the snappily-named GSK372475 doesn't work and has lots of side effects. It's a report of two clinicals trials in which Glaxo's contender was pitched against placebo and against older antidepressants in the treatment of depression.

GSK372475 failed to improve depression any better than placebo, even though the trials were large (393 and 504 patients respectively) and twice as long as most antidepressant trials (10 weeks whereas 4 or 6 is more usual)which ought to have given it plenty of room to shine.

The comparison drugs, the widely used venlafaxine and paroxetine, did work. A bit.

One of the trials even used the Bech "Melancholia Subscale" as an outcome measure, which Neuroskeptic readers may remember as I've praised it before. Venlafaxine worked on that, GSK's new pill didn't. If anything, the new drug was worse than placebo, in that patients improved slower.

In terms of side effects it caused dry mouth, insomnia, and nausea serious enough to make many people quit the study early. But even worse, it raised heart rate by almost 10 beats per minute on average, which is really never a good sign.

So, overall, it was an utter flop. In one sense this is not surprising. New "antidepressants" that don't work in trials have been all too common recently. Just last week we learned about the failure of "Serdaxin" in a Phase II trial. Actually Serdaxin isn't a new drug but an old antibiotic called clavulanic acid that a company was trying to rebrand as a mood lifter.

However the failure of GSK372475 is a bit of a mystery. The drug is a potent triple reuptake inhibitor (TRI) which acts on the neurotransmitters serotonin, noradrenaline and dopamine. By contrast, venlafaxine is a double reuptake inhibitor which doesn't hit dopamine, and paroxetine only targets serotonin. I've written about other TRIs before.

Now it seems surprising that venlafaxine worked, but a TRI didn't, in the same trial. That would imply that blocking the reuptake of dopamine makes you more depressed, enough to cancel out the other actions which are shared with venlafaxine. Which is not what I'd have predicted.

There are other differences between the drugs though. Venlafaxine has a very short half-life - it's broken down in the body in a matter of hours. But GSK372475 has a halflife of 8-10 days. Could this be the problem?

Learned S, Graff O, Roychowdhury S, Moate R, Krishnan KR, Archer G, Modell JG, Alexander R, Zamuner S, Evoniuk G, & Ratti E (2011). Efficacy, safety, and tolerability of a triple reuptake inhibitor GSK372475 in the treatment of patients with major depressive disorder: two randomized, placebo- and active-controlled clinical trials. Journal of psychopharmacology (Oxford, England) PMID: 22048884

The Teen Happiness Gene?

Whether you were happy with life as a teenager could be down to a certain gene, says a new study.

In a large study of American adolescents, the AddHealth project, teens who carried the long form of the 5HTTLPR locus were more likely to say they were satisfied or very satisified with their lives (at age 18 to 26). People with two long variants were the most cheerful, with short/long carriers in the middle and short/short being the least so.

The effect was significant controlling for ethnicity (p=0.013), however looking at the data shows that this effect was largely driven by the unhappy teens who reported being "Dissatisfied" or "Neither" on the 5 point scale of life satisfaction - but there were only a small number of these, because the great majority said they were "Satisfied" or "Very Satisfied". Still, there you go.

Incidentally, Neuroskeptic readers may remember AddHealth because of its role in the "black women are ugly" race row from earlier this year.

This study is the latest in a long, long line of attempts to correlate 5HTTLPR with happiness, depression, stress and so on. A few months ago I discussed the history of this busy little gene and covered a meta-analysis of no fewer than 54 papers which claimed that there was indeed a link, with the short allele increasing the risk of depression in response to stressful events.

However many studies failed to find one, and worryingly the three largest studies were all negative which is a classic tell-tale sign of publication bias - maybe people were only bothering to publish smaller studies if they did find a link and hence were "exciting findings". This is quite possible because so many researchers collect DNA as part of psychology studies these days. When the 5HTTLPR story got big (about 5 years ago) I know a lot of people decided to jump on the bandwagon by looking at it in the context of their old data.

Personally I have no idea whether 5HTTLPR is associated with anything. I used to think it probably did, but now I'm just confusion. There have been so many studies and so much inconsistency that it's very hard to know. What worries me is that I'm not sure whether we'll ever get a consensus. We've already had a gigantic study (over 80,000 people) showing no link and many meta-analyses coming to different conclusions.

What will it take to settle the issue? An even bigger study? Would 200,000 people do it? A million? I don't know.

De Neve JE (2011). Functional polymorphism (5-HTTLPR) in the serotonin transporter gene is associated with subjective well-being: evidence from a US nationally representative sample. Journal of human genetics, 56 (6), 456-9 PMID: 21562513

Life With Low Serotonin, Revisited

Last year I covered the case of a young man born with a genetic disorder which caused him to suffer low levels of the monoamine neurotransmitters - serotonin, dopamine, and noradrenaline.

These are the chemicals that are widely thought to be deficient in depression, and they're the target of antidepressant drugs (especially serotonin).

If low monoamines cause depression, you'd expect someone with low monoamines to be depressed, at least on the simplest view. But the case from last year had no reported mood problems, although he did show appetite, sleep and concentration problems that were cured by serotonin replacement therapy.

Now a new case report has just appeared that tells a different story. Gabriella Horvath and colleagues from British Columbia describe two sisters. Both had a normal birth and childhood, but at the ages of 11 and 15 respectively, began to suffer severe migraines and other symptoms. Sister 1:

started having hemiplegic migraine at age 11 years, initially occurring every 3–8 weeks, lasting 4–48 hours, presenting with right or left-sided numbness and paralysis, no visual disturbances, but slurred speech, associated with vomiting, headache, and confusion, followed by weakness lasting up to 7 days, and then complete recovery. The frequency of her migraine increased slowly with age up to twice a month...

Between 12 and 20 years she had developed progressive spastic paraparesis; sensory loss in stocking distribution... urinary and bowel incontinence; bladder instability... irritable bowel syndrome; sleep problems; depressed mood; and anxiety. She needed to use a wheelchair for most of the time by the age of 17.

Sister 2 had a rather different course:

The older sister originally presented at the age of 15 years with a history of hemiplegic migraine and seizures and myoclonic jerks. EEG showed generalized spike-and-wave activity, and polyspikes with photoconvulsive [light-induced seizures] response, in keeping with juvenile myoclonic epilepsy. Her seizures were brief and infrequent and not associated with the migraine episodes...

She subsequently developed progressive weakness, frequent falls, depression, and mild bladder instability...

Various blood and genetic tests failed to get to the bottom of it. MRI scans showed abnormalities in the spinal cord and parts of the brainstem in both cases, but why?

Spinal tap studies in Sister 1 revealed very low levels of 5HIAA, which is a by-product of brain serotonin (5HT). This suggested low 5HT levels. So doctors started her on 5HTP to try to boost it.

They report that 5HTP treatment caused "improvement" in all symptoms, including the migraines, slurred speech, depression, and movement, but not immediately. She gradually went from being in a wheelchair to being able to walk around the house on crutches, although she used a wheelchair outside. However, after 3 years of treatment, at age 20, she suddenly fell into a coma lasting 2 months. She is now recovering.

Sister 2 also had low 5HIAA, and was given 5HTP. She also reported symptomatic improvement.

Blood tests reported very low platelet serotonin levels. 5HTP treatment increased this but they were still below normal. Platelet 5HT reuptake rate was also low, suggesting a problem with the 5HT reuptake transporter protein 5HTT.

But the 5HTT gene (famously known as "The Happiness Gene" although that's questionable) seemed entirely normal in these patients. The authors say however that the symptoms are, in some ways, reminiscent of mice who lack the 5HT reuptake protein (5HTT knockout mice), who also show low serotonin. Also, if it were genetic, that wouldn't explain why there were no problems at all during childhood.

So this case is a mystery. The low serotonin has no known cause, and it might just be a side effect of a deeper underlying problem, but serotonin has long been linked to migraines so it might account for some of the symptoms. The fact that 5HTP helped supports this, though it wasn't a controlled trial so we can't know for sure.

As for the depression and anxiety, improved by 5HTP, this could have been a result of low serotonin, but it could also have been a psychological reaction to the severe medical problems. It's impossible to know.

Horvath GA, Selby K, Poskitt K, Hyland K, Waters PJ, Coulter-Mackie M, & Stockler-Ipsiroglu SG (2011). Hemiplegic migraine, seizures, progressive spastic paraparesis, mood disorder, and coma in siblings with low systemic serotonin. Cephalalgia : an international journal of headache PMID: 22013141

New Antidepressant - Old Tricks

The past decade has been a bad one for antidepressant manufacturers.

Quite apart from all the bad press these drugs have been getting lately, there's been a remarkable lack of new antidepressants making it to the market. The only really novel drugs to hit the shelves since 2000 have been agomelatine and vilazodone. There were a couple of others that were just minor variants on old molecules, but that's it. Quite a contrast from the 1990s when new drugs were ten-a-penny.

This makes "Lu AA21004" rather special. It's a new antidepressant currently in development and by all accounts it's making good progress. It's now in Phase III trials, the last stage before approval. And a large clinical trial has just been published finding that it works.

But is it a medical advance or merely a commercial one?

Pharmacologically, Lu AA21004 is kind of a new twist on an old classic . Its main mechanism of action is inhibiting the reuptake of serotonin, just like Prozac and other SSRIs. However, unlike them, it also blocks serotonin 5HT3 and 5HT7 receptors, activates 5HT1A receptors and partially agonizes 5HT1B.

None of these things cry out "antidepressant" to me, but they do at least make it a bit different.

The new trial took 430 depressed people and randomized them to get Lu AA21004, at two different doses, 5mg or 10mg, or the older antidepressant venlafaxine at the high-ish dose of 225 mg, or placebo.

It worked. Over 6 weeks, people on the new drug improved more than those on placebo, and equally as well as people on venlafaxine; the lower 5 mg dose was a bit less effective, but not significantly so.

The size of the effect was medium, with a benefit over-and-above placebo of about 5 points on the MADRS depression scale, which considering that the baseline scores in this study averaged 34, is not huge, but it compares well to other antidepressant trials.

Now we come to the side effects, and this is the most important bit, as we'll see later. The authors did not specifically probe for these, they just relied on spontaneous report, which tends to underestimate adverse events.


Basically, the main problem with Lu AA21004 was that it made people sick. Literally - 9% of people on the highest dose suffered vomiting, and 38% got nausea. However, the 5 mg dose was no worse than venlafaxine for nausea, and was relatively vomit-free. Unlike venlafaxine, it didn't cause dry mouth, constipation, or sexual problems.

So that's lovely then. Let's get this stuff to market!

Hang on.

The big selling point for this drug is clearly the lack of side effects. It was no more effective than the (much cheaper, because off-patent) venlafaxine. It was better tolerated, but that's not a great achievement to be honest. Venlafaxine is quite notorious for causing side effects, especially at higher doses.

I take venlafaxine 300 mg and the side effects aren't the end of the world, but they're no fun, and the point is, they're well known to be worse than you get with other modern drugs, most notably SSRIs.

If you ask me, this study should have compared the new drug to an SSRI, because they're used much more widely than venlafaxine. Which one? How about escitalopram, a drug which is, according to most of the literature, one of the best SSRIs, as effective as venlafaxine, but with fewer side effects.

Actually, according to Lundbeck, who make escitalopram, it's even better than venlafaxine. Now, they would say that, given that they make it - but the makers of Lu AA21004 ought to believe them, because, er, they're the same people. "Lu" stands for Lundbeck.

The real competitor for this drug, according to Lundbeck, is escitalopram. But no-one wants to be in competition with themselves.

This may be why, although there are no fewer than 26 registered clinical trials of Lu AA21004 either ongoing or completed, only one is comparing it to an SSRI. The others either compare it to venlafaxine, or to duloxetine, which has even worse side effects. The one trial that will compare it to escitalopram has a narrow focus (sexual dysfunction).

Pharmacologically, remember, this drug is an SSRI with a few "special moves", in terms of hitting some serotonin receptors. The question is - do those extra tricks actually make it better? Or is it just a glorified, and expensive, new SSRI? We don't know and we're not going to find out any time soon.

If Lu AA21004 is no more effective, and no better tolerated, than tried-and-tested old escitalopram, anyone who buys it will be paying extra for no real benefit. The only winner, in that case, being Lundbeck - especially given that escitalopram goes off-patent in 2012...

Alvarez E, Perez V, Dragheim M, Loft H, & Artigas F (2011). A double-blind, randomized, placebo-controlled, active reference study of Lu AA21004 in patients with major depressive disorder. The International Journal of Neuropsychopharmacology , 1-12 PMID: 21767441

Revenge Of The Depression Gene

Last year, the world of psychiatric genetics was rocked by the news that a highly-studied gene, believed to be associated with depression, wasn't in fact linked to depression at all.

The genetic variant was 5-HTTLPR. It's a length variant in the gene coding for the serotonin transporter protein (5HTT) which the target of antidepressants like Prozac. There are two flavors of this variant, short and long.

Many studies have shown that the short ("s") variant is associated with a high risk of getting depression in response to stress - but then last year a large meta-analysis of all the evidence concluded that there was in reality no link. Bummer.

Now another team of researchers have done a new analysis of the 5-HTTLPR & stress & depression data and they claim that there is a link after all: hooray! So who's right? I'm not sure, but the new paper raises many questions.

The new paper puts together the results of all 54 studies which have looked at this gene in the context of depression, caused by any kind of stress. The authors were intentionally liberal in their inclusion criteria: studies in any population were OK, for example they included people with Parkinson's disease or heart disease.

They say that this is the main difference between the present work and earlier meta-analyses that found no link. The famous 2010 paper, for example, only included 14 studies because they only considered certain kinds of stress.

Anyway, the short variant is associated with depression after all, across all of the studies. They extracted the p values from the results of all previous studies, and took the average of those, weighted by the sample size. They found a very significant association: P=.00002.

Here's all the results. Each square is a study, the further to the left, the more strongly they found an association. Bigger squares mean larger studies. As you can see, most studies found a link but the three largest studies - which were much larger than the others - found none. Hmm.

In terms of specific kinds of stress, they found strong evidence that "specific stressors" (like medical illness), and childhood trauma, were associated with more depression in s-allele carriers. However, in the studies on "Stressful Life Events", which is a broad category meaning pretty much anything bad that happens, the evidence was weaker. The previous meta-analyses only considered these studies.

Ultimately, I think this analysis should remind us that the issue of 5HTTLPR is still "open", but I have concerns about the dataset. The fact that larger studies seem less likely to be positive is a classic warning sign of publication bias.

The authors do consider this and say that they calculate that there would have to be over 700 unpublished, negative studies out there, in order to make the overall data negative. They also find that you could ignore the smallest 45 studies and still find a result. But still. Something doesn't feel right. Maybe I just have the wrong 5HTTLPR variant.

Karg K, Burmeister M, Shedden K, & Sen S (2011). The Serotonin Transporter Promoter Variant (5-HTTLPR), Stress, and Depression Meta-analysis Revisited: Evidence of Genetic Moderation. Archives of general psychiatry, 68 (5), 444-54 PMID: 21199959

Blue Morning

Recently, I wrote about diurnal mood variation: the way in which depression often waxes and wanes over the course of the day. Mornings are generally the worst.

A related phenomenon is late insomnia, or "early morning waking".

But this phrase is rather an understatement. Everyone's woken up early. Maybe you had a flight to catch. Or you were drunk and threw up. Or you just needed a pee. That's early morning waking, but not the depressive kind. When you're depressed, the waking up is the least of your problems.

Suddenly, you are awake, more awake than you've ever been. And you know something terrible has happened, or is about to happen, or that you've done something terribly wrong. It feels like a Eureka moment. You can be a level-headed person, not given to jumping to conclusions, but you will be convinced of this.

In a panic attack, you think you're going to die. Your heart is beating too fast, your breathing's too deep: your body is exploding, you can feel it too closely. With this, With this, you think you should die or even, in some sense, already have. It feels cold: you can no longer feel the warmth of your own body.

The moment passes; the terrible truth that you were so certain of five minutes ago becomes a little doubtful. Maybe it's not quite so bad. At this point, the wakefulness goes too, and you become, well, as tired as you ought to be at 3 am. You try to go back to sleep. If you're lucky, you succeed. If not, you lie awake until morning in a state of miserable contemplation.

While it's happening, you think that you're going to feel this way forever; bizarrely, you think you always have felt this way. In fact, this is the darkest hour.

*

Why does this happen? There has been almost no research on early morning waking. Presumably, because it's so hard to study. To observe it, you would have to get your depressed patients to spend all night in your brain scanner (or, if you prefer, on your analyst's couch), and even then, it doesn't happen every night.

But here's my theory: the key is the biology of sleep. There are many stages of sleep; at a very rough approximation there's dreaming REM, and dreamless slow-wave. Now, REM sleep tends to happen during the second half of the night - the early morning.

During REM sleep, the brain is, in many respects, awake. This is presumably what allows us to have concious dreams. Whereas in slow wave sleep, the brain really is offline; slow waves are also seen in the brain of people in comas, or under deep anaesthesia.

When we're awake, the brain is awash with modulatory neurotransmitters, such as serotonin, norepinephrine, and acetylcholine. During REM, acetylcholine is present, while in slow-wave sleep it's not; indeed acetylcholine may well be what stops slow waves and "wakes up" the cortex.

But unlike during waking, serotonin and norepinephrine neurons are entirely inactive during REM sleep - and only during REM sleep. This fact is surprisingly little-known, but it seems to me that it explains an awful lot.

For one thing, it explains why drugs which increase serotonin levels, such as SSRI antidepressants, inhibit REM sleep. Indeed, high doses of MAOi antidepressants prevent REM entirely (without any noticeable ill-effects, suggesting REM is dispensable). SSRIs only partially suppress it.

Ironically, SSRIs can make dreams more vivid and colourful. I've been told by sleep scientists that this is because they delay the onset of REM so the dreams are "shifted" later into the night making you more likely to remember them when you wake up. But there could be more to it than that.

The fact that REM is a serotonin-free zone also explains wet dreams. Serotonin is well known to suppresses ejaculation; that's why SSRIs delay orgasm, one of their least popular side effects, although it's useful to treat premature ejaculation: every cloud has a silver lining.

So, having said all that: could this also explain the terror of early-morning waking? Suppose that, for whatever reason, you woke up during REM sleep, but your serotonin cells didn't wake up quick enough, leaving you awake, but with no serotonin (a situation which never normally occurs, remember). How would that feel?

Using a technique called acute tryptophan depletion (ATD), you can lower someone's serotonin levels. In most people, this doesn't do very much, but in some people with a history of depression, it causes them to relapse. Here's what happened to one patient after ATD:

[her] previous episodes of clinical depression were associated with the loss of important friendships had, while depressed, been preoccupied with fears that she would never be able to sustain a relationship. She had not had such fears since then.

She had been fully recovered and had not taken any medication for over a year. About 2 h after drinking the tryptophan-free mixture she experienced a sudden onset of sadness, despair, and uncontrollable crying. She feared that a current important relationship would end.

We don't know why tryptophan depletion does this to some people, or why it doesn't affect everyone the same way, and it's pure speculation that early morning waking has anything to do with this. But having said that, the pieces do seem to fit.

The Hunt for the Prozac Gene

One of the difficulties doctors face when prescribing antidepressants is that they're unpredictable.

One person might do well on a certain drug, but the next person might get no benefit from the exact same pills. Finding the right drug for each patient is often a matter of trying different ones until one works.

So a genetic test to work out whether a certain drug will help a particular person would be really useful. Not to mention really profitable for whoever patented it. Three recent papers, published in three major journals, all claim to have found genes that predict antidepressant response. Great! The problem is, they were different genes.

First up, American team Binder et al looked at about 200 variants in 10 genes involved in the corticosteroid stress response pathway. They found one, in a gene called CRHBP, that was significantly associated with poor response to the popular SSRI antidepressant citalopram (Celexa), using the large STAR*D project data set. But this was only true of African-Americans and Latinos, not whites.

Garriock et al used the exact same dataset, but they did a genome-wide association study (GWAS), which looks at variants across the whole genome, unlike Binder et al who focussed on a small number of specific candidate genes. Sadly no variants were statistically significantly correlated with response to citalopram, although in a GWAS, the threshold for genome-wide significance is very high due to multiple comparisons correction. Some were close to being significant, but they weren't obviously related to CRHBP, and most weren't anything to do with the brain.

Uher et al did another GWAS of response to escitalopram and nortriptyline in a different sample, the European GENDEP study. Escitalopram is extremely similar to citalopram, the drug in the STAR*D studies; nortriptyline however is very different. They found one genome-wide significant hit. A variant in a gene called UST was associated with response to nortriptyline, but not escitalopram. No variants were associated with response to escitalopram, although one in the gene IL11 was close. There were some other nearly-significant results, but they didn't overlap with either of the STAR*D studies.

Finally, one of the STAR*D studies found a variant significantly linked to tolerability (side effects) of citalopram. GENDEP didn't look at this.

*

The UST link to nortriptyline finding is the strongest thing here, but for citalopram / escitalopram, no consistent pharmacogenetic results emerged at all. What does this mean? Well, it's possible that there just aren't any genes for citalopram response, but that seems unlikely. Even if you believe that antidepressants only work as placebos, you'd expect there would be genes that alter placebo responses, or at the very least, that affect side-effects and hence the active placebo improvement.

The thing is that the "antidepressant response" in these studies isn't really that: it's a mix of many factors. We know that a lot of the improvement would have happened even with placebo pills, so much of it isn't a pharmacological effect. There are probably genes associated with placebo improvement, but they might not be the same ones that are associated with drug improvement and a gene might even have opposite effects that cancel out (better drug effect, worse placebo effect). Some of the recorded improvement won't even be real improvement at all, just people saying they feel better because they know they're expected to.

If I were looking for the genes for SSRI response, not that I plan to, here's what I'd do. To stack the odds in my favour, I'd forget people with an moderate or partial response, and focus on those who either do really well, or those who get no benefit at all, with a certain drug. I'd also want to exclude people who respond really well, but not due to the specific effects of the drug.

That would be hard but one angle would be to only include people whose improvement is specifically reversed by acute tryptophan depletion, which reduces serotonin levels thus counteracting SSRIs. This would be a hard study to do, though not impossible. (In fact there are dozens of patients on record who meet my criteria, and their blood samples are probably still sitting in freezers in labs around the world... maybe someone should dig them out).

Still, even if you did find some genes that way, would they be useful? We'd have had to go to such lengths to find them, that they're not going to help doctors decide what to do with the average patient who comes through the door with depression. That's true, but they might just help us to work out who will respond to SSRIs, as opposed to other drugs.

Binder EB, Owens MJ, Liu W, Deveau TC, Rush AJ, Trivedi MH, Fava M, Bradley B, Ressler KJ, & Nemeroff CB (2010). Association of polymorphisms in genes regulating the corticotropin-releasing factor system with antidepressant treatment response. Archives of general psychiatry, 67 (4), 369-79 PMID: 20368512

Uher, R., Perroud, N., Ng, M., Hauser, J., Henigsberg, N., Maier, W., Mors, O., Placentino, A., Rietschel, M., Souery, D., Zagar, T., Czerski, P., Jerman, B., Larsen, E., Schulze, T., Zobel, A., Cohen-Woods, S., Pirlo, K., Butler, A., Muglia, P., Barnes, M., Lathrop, M., Farmer, A., Breen, G., Aitchison, K., Craig, I., Lewis, C., & McGuffin, P. (2010). Genome-Wide Pharmacogenetics of Antidepressant Response in the GENDEP Project American Journal of Psychiatry DOI: 10.1176/appi.ajp.2009.09070932

Garriock, H., Kraft, J., Shyn, S., Peters, E., Yokoyama, J., Jenkins, G., Reinalda, M., Slager, S., McGrath, P., & Hamilton, S. (2010). A Genomewide Association Study of Citalopram Response in Major Depressive Disorder Biological Psychiatry, 67 (2), 133-138 DOI: 10.1016/j.biopsych.2009.08.029

Life Without Serotonin

Via Dormivigilia, I came across a fascinating paper about a man who suffered from a severe lack of monoamine neurotransmitters (dopamine, serotonin etc.) as a result of a genetic mutation: Sleep and Rhythm Consequences of a Genetically Induced Loss of Serotonin


Neuroskeptic readers will be familiar with monoamines. They're psychiatrists' favourite neurotransmitters, and are hence very popular amongst psych drug manufacturers. In particular, it's widely believed that serotonin is the brain's "happy chemical" and that clinical depression is caused by low serotonin while antidepressants work by boosting it.

Critics charge that there is no evidence for any of this. My own opinion is that it's complicated, but that while there's certainly no simple relation between serotonin, antidepressants and mood, they are linked in some way. It's all rather mysterious, but then, the functions of serotonin in general are; despite 50 years of research, it's probably the least understood neurotransmitter.

The new paper adds to the mystery, but also provides some important new data. Leu-Semenescu et al report on the case of a 28 year old man, with consanguineous parents, who suffers from a rare genetic disorder, sepiapterin reductase deficiency (SRD). SRD patients lack an enzyme which is involved, indirectly, in the production of the monoamines serotonin and dopamine, and also melatonin and noradrenaline which are produced from these two. SRD causes a severe (but not total) deficiency of these neurotransmitters.

The most obvious symptoms of SRD are related to the lack of dopamine, and include poor coordination and weakness, very similar to Parkinson's Disease. An interesting feature of SRD is that these symptoms are mild in the morning, worsen during the day, and improve with sleep. Such diurnal variation is also a hallmark of severe depression, although in depression it's usually the other way around (better in the evening).

The patient reported on in this paper suffered Parkinsonian symptoms from birth, until he was diagnosed with dystonia at age 5 and started on L-dopa to boost his dopamine levels. This immediately and dramatically reversed the problems.

But his serotonin synthesis was still impaired, although doctors didn't realize this until age 27. As a result, Leu-Semenescu et al say, he suffered from a range of other, non-dopamine-related symptoms. These included increased appetite - he ate constantly, and was moderately obese - mild cognitive impairment, and disrupted sleep:

The patient reported sleep problems since childhood. He would sleep 1 or 2 times every day since childhood and was awake during more than 2 hours most nights since adolescence. At the time of the first interview, the night sleep was irregular with a sleep onset at 22:00 and offset between 02:00 and 03:00. He often needed 1 or 2 spontaneous, long (2- to 5-h) naps during the daytime.

After doctors did a genetic test and diagnosed SRD, they treated him with 5HTP, a precursor to serotonin. The patient's sleep cycle immediately normalized, his appetite was reduced and his concentration and cognitive function improved (although that may have been because he was less tired). Here's his before and after hypnogram:

Disruptions in sleep cycle and appetite are likewise common in clinical depression. The direction of the changes in depression varies: loss of appetite is common in the most severe "melancholic" depression, while increased appetite is seen in many other people.

For sleep, both daytime sleepiness and night-time insomnia, especially waking up too early, can occur in depression. The most interesting parallel here is that people with depression often show a faster onset of REM (dreaming) sleep, which was also seen in this patient before 5HTP treatment. However, it's not clear what was due to serotonin and what was due to melatonin because melatonin is known to regulate sleep.

Overall, though, the biggest finding here was a non-finding: this patient wasn't depressed, despite having much reduced serotonin levels. This is further evidence that serotonin isn't the "happy chemical" in any simple sense.

On the other hand, the similarities between his symptoms and some of the symptoms of depression suggest that serotonin is doing something in that disorder. This fits with existing evidence from tryptophan depletion studies showing that low serotonin doesn't cause depression in most people, but does re-activate symptoms in people with a history of the disease. As I said, it's complicated...

Smaranda Leu-Semenescu et al. (2010). Sleep and Rhythm Consequences of a Genetically Induced Loss of Serotonin Sleep, 33 (03), 307-314

Predicting Antidepressant Response with EEG

One of the limitations of antidepressants is that they don't always work. Worse, they don't work in an unpredictable way. Some people benefit from some drugs, and others don't, but there's no way of knowing in advance what will happen in any particular case - or of telling which pill is right for which person.

As a result, drug treatment for depression generally involves starting with a cheap medication with relatively mild side-effects, and if that fails, moving onto a series of other drugs until one helps. But since it can take several weeks for any new drug to work, this can be a frustrating process for patients and doctors alike.

Some means of predicting the antidepressant response would thus be very useful. Many have been proposed, but none have entered widespread clinical use. Now, a pair of papers(1,2) from UCLA's Andrew Leuchter et al make the case for prediction using quantitative EEG (QEEG).

EEG, electroencephalography, is a crude but effective way of recording electrical activity in the brain via electrodes attached to the head. "Quantitative" EEG just means using EEG to precisely measure the level of certain kinds of activity in the brain.

Leuchter et al's system is straightforward: it uses six electrodes on the front of the head. The patient simply relaxes with their eyes closed for a few minutes while neural activity is recorded.

This procedure is performed twice, once just before antidepressant treatment begins and then again a week later. The claim is that by examining the changes in the EEG signal after one week of drug treatment, the eventual benefit of the drug can be predicted. It's not an implausible idea, and if it did work, it would be rather helpful. But does it?

Leuchter et al say: yes! The first paper reports that in 73 depressed patients who were given the antidepressant escitalopram 10mg/day, QEEG changes after one week predicted clinical improvement six weeks later. Specifically, people who got substantially better at seven weeks had a higher "Antidepressant Treatment Response Index" (ATR) at one week than people who didn't: 59.0 ± 10.2 vs 49.8 ± 7.8, which is highly significant (p less than 0.001).

In the companion paper, the authors examined patients who started on escitalopram and then either kept taking it or switched to a different antidepressant, bupropion. They found that patients who had a high ATR after a week of escitalopram tended to do well if they stayed on it, while patients who had a low ATR to escitalopram did better when they switched to the other drug.

These are interesting results, and they follow from ten years of previous work (mostly, but not exclusively, from the same group) on the topic. Because the current study didn't include a placebo group, we can't say that the QEEG predicts antidepressant response as such, only that it predicts improvement in depression symptoms. But even this is pretty exciting, if it really works.

In order to verify that it does, other researchers need to replicate this experiment. But they may find this a little difficult. What is the Antidepressant Treatment Response Index use in this study? It's derived from an analysis of the EEG signal, and we're told that you get it from this formula:

Some of the terms here are common parameters that any EEG expert will understand. But "A", "B", and "C" are not. They're constants, which are not given in the paper. They're secret numbers. Without knowing what those numbers are, no-one can calculate the "ATR" even if they have an EEG machine.

Why keep them secret? Well...

"Financial support of this project was provided by Aspect Medical Systems. Aspect participated in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation and review of the manuscript."

Aspect is a large medical electronics company who developed the system used here. Presumably, they want to patent it (or already have). We're told that

"To facilitate independent replication of the work reported here, Aspect intends to make available a limited number of investigational systems for academic researchers. Please contact Scott Greenwald, Ph.D... for further information."

All very nice of them, but if they'd told us the three magic numbers, academics could start trying to independently replicate these results tomorrow. As it is, anyone who wants to do so will have to get Aspect's blessing, which, with the best will in the world, means they will not be entirely "independent".

[BPSDB]

Leuchter AF, Cook IA, Gilmer WS, Marangell LB, Burgoyne KS, Howland RH, Trivedi MH, Zisook S, Jain R, Fava M, Iosifescu D, & Greenwald S (2009). Effectiveness of a quantitative electroencephalographic biomarker for predicting differential response or remission with escitalopram and bupropion in major depressive disorder. Psychiatry research PMID: 19709754

Leuchter AF, Cook IA, Marangell LB, Gilmer WS, Burgoyne KS, Howland RH, Trivedi MH, Zisook S, Jain R, McCracken JT, Fava M, Iosifescu D, & Greenwald S (2009). Comparative effectiveness of biomarkers and clinical indicators for predicting outcomes of SSRI treatment in Major Depressive Disorder: Results of the BRITE-MD study. Psychiatry research PMID: 19712979