Upcoming Appearances (And A Funny Picture)

Just a quick reminder - or perhaps a new announcement for those of you who aren't on Twitter - that I've been short-listed for the UK Science Blogging Prize. I'll be giving a very brief talk at the awards night next Sunday 25th November which is in the Penderel's Oak, London.

Speaking of Twitter, I'm on Twitter here: https://twitter.com/Neuro_Skeptic

I'll also be speaking in Philadelphia on December 6th at UPenn on the topic of Brain Rumors: Public (MIs)understanding of Neuroscience and Why It Matters

Finally, to save this from being a completely boring post, here is the cover of the latest British Medical Journal, which in my opinion is the funniest image ever to grace the front of an academic publication. Even if it is, literally, potty humour.

We're Probably Not Getting Dumber

There's been buzz over the past few days in the idea that humans have been getting stupider for the past few millennia. That's according to Stanford's Gerald R. Crabtree -

I would wager that if an average citizen from Athens of 1000 BC were to appear suddenly among us, he or she would be among the brightest and most intellectually alive of our colleagues and companions, with a good memory, a broad range of ideas, and a clear-sighted view of important issues. Furthermore, I would guess that he or she would be among the most emotionally stable of our friends and colleagues.

OK. How so?

Crabtree's argument in a nutshell:

In Part I, he outlines the latest evidence showing that many thousands of genes contribute to human cognitive ability, and that because mutation rates are high (higher than previously believed), any given individual probably carries harmful variants of many of these genes. This is quite possibly true ,and interesting, but by itself it's nothing to do with declining IQ.

In Part II, Crabtree says that during human evolution, all of these genes were under strong selection pressure because any human or proto-human who wasn't smart enough to hunt, fight and survive in the stone age environment, would get eaten by a predator or starve. However, after these hunter-gatherer tribes became settled farming communities (in say 6000 BC), they were no longer so vulnerable, so the less intellectually able could live... and breed... leading to ever-more unintelligence genes.

Now, there's a lot of problems here. Many have said that this is all a bit like eugenics, and indeed it is, but that doesn't necessary mean it's wrong... no, it's wrong because the argument is flawed.

For instance, it's already been pointed out that, even if it recently got easier to stay alive, that doesn't mean it's got easier to get laid lots and have lots of kids; and sexual selection is a powerful force in evolution, perhaps even stronger than survival, and it probably favours higher intelligence.

However, there are other issues.

The idea that hunter-gatherers have especially hard lives is dubious. There's good evidence that life expectancy and health fell when hunter-gatherer societies settled down and got agriculture. Today, survival doesn't exert much of a selective pressure in most parts of the world but life stayed pretty precarious (by modern standards) until at least the 19th century.  You could indeed argue that 8,000-odd years of agriculture made us smarter than ever before, and that we're enjoying the benefits . In which case we'd be smarter than someone from 1000 BC, who only had 5,000 years or so.

Crabtree does acknowledge that agriculture changed selection pressures. He suggests that it would have made it more important to be immune to the various diseases that emerged when our population density rose. But this isn't enough - for his argument to work, intelligence would also have needed to become less important with agriculture, and whether that's true is really not clear at all. Maybe it did. Maybe it didn't. There's a prejudice in modern culture against 'ignorant peasants' and 'dumb hicks', but farming is not easy.

Even if we do grant that cognitive evolutionary pressures have eased since 1000 BC, it's not clear that this would make us 'less intelligent'. 'Intelligence' is not one thing. To simplify, it might be that there's a trade-off between 'book smarts' and 'street smarts', and that you used to need the latter to survive. A society in which everyone survives would then allow more people the luxury of being book-smart. Would Einstein or Newton would have made good peasants?

Crabtree's arguments are interesting, but they're entirely speculative. There's just no hard evidence for the decline of intelligence over recent millennia. Since we can't go back in time and do IQ tests, there never will be, although he does suggest an experiment, using genetics, that might be able to check whether there's been a build-up of harmful mutations.

But until then, as he puts it,

in the meantime I’m going to have another beer and watch my favorite rerun of ‘Miami CSI’ (if I can figure out how to work the remote control).

Crabtree, G. (2012). Our fragile intellect. Part II Trends in Genetics DOI: 10.1016/j.tig.2012.10.003 

Crabtree, G. (2012). Our fragile intellect. Part I Trends in Genetics DOI: 10.1016/j.tig.2012.10.002

The New "Mood Disorder" That Isn't One

The storied history of "Disruptive Mood Dysregulation Disorder (DMDD)", a controversial new child psychiatric disorder proposed for inclusion in the new DSM-5 manual, continues.

If DSM-5 is officially published (it's due in 2013), kids will be deemed DMDD if they show

severe recurrent temper outbursts that are grossly out of proportion in intensity or duration to the situation.

At least three times a week. Would giving that label be helpful?

Pittsburg psychiatrists David Axelson and colleagues have just shown that the DMDD concept is deeply flawed. They took a large sample of kids assessed for emotional or behavior problems, and compared those who would meet the new DMDD criteria, to those who wouldn't.

"DMDD" turned out not to be correlated with anxiety or mood symptoms in either the child or their parents - rather unusual for a so-called 'Mood Dysregulation Disorder' which is found in the 'Depressive Disorder' section of the DSM-5.

However, DMDD was correlated with - and in fact "could not be delimited from" - two existing disorders, "Conduct Disorder" and "Oppositional Defiant Disorder". It wasn't even a more severe form of those disorders, it was pretty much the same thing.

So, DMDD seems to be nothing to do with mood, but instead covers a pattern of misbehavior which is already covered by not one but two labels already. Why add a misleadingly-named third?

Well, the back-story is that in the past ten years, many American kids and even toddlers have got  diagnosed with 'child bipolar disorder'  - a disease considered extremely rare everywhere else. To stop this, the DSM-5 committee want to introduce DMDD as a replacement. This is the officially stated reason for introducing it. On the evidence of this paper and others it wouldn't even achieve this dubious goal.

The possibility of just going to back to the days when psychiatrists didn't diagnose prepubescent children with bipolar (except in very rare cases) seems to not be on the table.

Axelson D, et al (2012). Examining the proposed disruptive mood dysregulation disorder diagnosis in children in the Longitudinal Assessment of Manic Symptoms study. The Journal of Clinical Psychiatry, 73 (10), 1342-50 PMID: 23140653

Beware Small Positive Studies

A Letter in the prestigious American Journal of Psychiatry offers a skeptical response to a paper published there recently.

The original article claimed amazing benefits of a safe and cheap brain stimulation technique in treating schizophrenia. But Dutch letter-writers Sommer et al aren't convinced.

It's a short piece and worth quoting:

We read with interest the article by Brunelin et al. in the July issue, which described the application of transcranial direct-current stimulation (tDCS) in the treatment of both auditory hallucinations and negative symptoms simultaneously... An effect size of 1.58 was reported for refractory hallucinations, which is remarkably large when compared with the effect sizes of antipsychotic medication (0.4–0.6).

Clinical trials involving nonconvulsive brain stimulation in schizophrenia were first introduced in 1999. Initial effect sizes were very large while samples were small. Some years later, large negative studies were published. To date, 17 placebo controlled transcranial magnetic stimulation (TMS) studies on hallucinations have been published. The mean weighted effect size is now around 0.3. Yet, the negative correlation between effect size and year of publication suggests that over time, the mean effect size may become smaller.

When selective serotonin reuptake inhibitors (SSRIs) were introduced for depression, effect sizes greater than 1.0 were reported, which created their legacy as a wonder drug. Over the course of 20 years, the mean effect size of SSRIs decreased to around 0.3. A similar trend was demonstrated for cognitive-behavioral therapy.
 
This trend likely results from publication bias. A remarkably high effect size suggests the discovery of a new wonder treatment. Studies with such findings are therefore easily published in high-impact journals. In contrast, studies of similar sample size with marginally or nonsignificant findings are less likely to be accepted for publication. Usually, after some years, negative studies with large sample sizes become available. This is when meta-analyses start to detect a decrease in efficacy.

In this view, the Brunelin et al. study is exemplary of an initial placebo-controlled study applying a new technique: it included a small sample, found remarkably large effects, and is published in a high-impact journal.
 
We sincerely hope that tDCS is the exception to the rule— as a cheap, safe, and highly effective method to treat both refractory hallucinations and negative symptoms is most welcome. However, given the previous observations for other new treatments, it is realistic to expect that 10 years from now the mean weighted effect size of tDCS will be around 0.3.

Sommer et al are talking about the famous 'decline effect', in which the size of an effect mysteriously shrinks the more people study it, which I've written about before.

I suspect the authors are right in this case; playing science devil's advocate though, it's unfair and unscientific to assume that a new treatment that looks promising will eventually turn out to be mediocre, just because that's happened to other treatments before.

After all, some things look awesome because they are - penicillin, for example, was heralded as a new wonder drug... and it was.

I very much doubt that tDCS is the new penicillin. But I do think that this kind of speculation is ultimately not very useful. Rather than bemoaning the errors of the past and wondering whether they'll be repeated, we should reform science to make sure they don't.

Sommer IE, Aleman A, Slotema CM, and Schutter DJ (2012). Transcranial stimulation for psychosis: the relationship between effect size and published findings. The American Journal of Psychiatry, 169 (11) PMID: 23128925

Migraines On Twitter

People talk about migraines on Twitter more on weekdays than weekends and holidays - and the peak time of day for the horrible headaches is 7 in the morning.

The working-day effect on migraines has been reported before - perhaps a reflection of stress or, less charitably, people wanting a day off work... although some people suffer weekend migraines.

Of the working week, Tuesdays saw the most migraines, while Fridays were the least bad. About 80% of Twitter migraine mentions came from women - which matches the fact that women are at higher risk.

That's according to a little study just published that used a public database of tweets, timeu.se, that Neuroskeptic readers may remember.

In fact, an author of this study said in an email to me that it was actually inspired by one of my posts... but I'm aware that telling you that, combined with the previous post, means I'm in danger of blowing my own trumpet or 'disappearing up my own arse' as we say in the UK. So rest assured that this will be the last such self-referential piece for at least... a day or two.

Linnman, C., Maleki, N., Becerra, L., and Borsook, D. (2012). Migraine Tweets - What can online behavior tell us about disease? Cephalalgia DOI: 10.1177/0333102412465207