Exercise and Depression: It's Complicated

Some ideas seem so nice, so inoffensive and so harmless, that it seems a shame to criticize them.

Take the idea that exercise is a useful treatment for depression. It's got something for everyone.

For doctors, it's attractive because it means they can recommend exercise - which is free, quick, and easy, at least for them - instead of spending the time and money on drugs or therapy. Governments like it for the same reason, and because it's another way of improving the nation's fitness. For people who don't much like psychiatry, exercise offers a lovely alternative to psych drugs - why take those nasty antidepressants if exercise will do just as well? And so on.

But this doesn't mean it's true. And a large observational study from Norway has just cast doubt on it: Physical activity and common mental disorders.

The authors took a large community sample of Norwegian people, the HUNT-2 study, which was done between 1995 and 1997. Over 90,000 people were invited to take part and full data were available from over 40,000.

What they found was that there was an association between taking part in physical exercise as a leisure activity, and lower self-reported symptoms of depression. It didn't matter whether the activity was intense or mild, and it didn't really matter how often you did it: so long as you did it, you got the benefit.

Crucially, however, the same was not true of physical exercise which was part of your job. That didn't help at all, and indeed the most strenuous jobs were associated with more depression (but less anxiety, strangely).

How does this fit with the very popular idea that exercise helps in depression? Well, many randomized trials have indeed shown exercise to be better than not-exercize for depression, but the problem is that these trials are never really placebo controlled. You can usually tell whether or not you're going jogging in the park every morning.

So the direct effects of exercise per se are hard to distinguish from the social and psychological meaning of "exercise". Knowing that you're starting a program of exercise could make you feel better: you're taking positive action to improve your life, you're not helpless in the face of your problems. By contrast, doing heavy work as part of your job, while physiologically beneficial, is unlikely to be so much fun.

This doesn't mean that telling people to get more exercise isn't a good idea, but if the meaning of exercise is more important than the physiology, that has some big implications for how it ought to be used.

It's good news for people who just can't take part in strenuous physical exercise because of physical illness or disability, something which is quite common in mental health. It suggests that these people could still get the benefits attributed to exercise even if they did less demanding forms of meaningful activity.

But it's bad news for doctors tempted to default to "get out and go jogging" whenever they see a potentially depressed person. Because if it's the meaning of exercise that counts, and you recommend exercise in a way which sounds like you're dismissing their problems, the meaning will be anything but helpful.

In clinical trials of exercise, the exercise program has, almost by definition, a positive value: it's the whole point of the trial. And the participants just wouldn't have volunteered for the trial if they didn't, on some level, think it would make them feel better.

But not everyone thinks that way. If you go to your doctor looking to get medication, or psychotherapy, or something like that, and you're told that all you need to do is go and get more exercise, it would be easy to see that as a brush-off, especially if it's done unsympathetically. The point is, if exercise doesn't feel like a positive step, it probably won't be one.

Harvey SB, Hotopf M, Overland S, & Mykletun A (2010). Physical activity and common mental disorders. The British journal of psychiatry : the journal of mental science, 197, 357-64 PMID: 21037212

The Town That Went Mad

Pont St. Esprit is a small town in southern France. In 1951 it became famous as the site of one of the most mysterious medical outbreaks of modern times.

As Dr's Gabbai, Lisbonne and Pourquier wrote to the British Medical Journal, 15 days after the "incident":

The first symptoms appeared after a latent period of 6 to 48 hours. In this first phase, the symptoms were generalized, and consisted in a depressive state with anguish and slight agitation.

After some hours the symptoms became more clearly defined, and most of the patients presented with digestive disturbances... Disturbances of the autonomic nervous system accompanied the digestive disorders-gusts of warmth, followed by the impression of "cold waves", with intense sweating crises. We also noted frequent excessive salivation.

The patients were pale and often showed a regular bradycardia (40 to 50 beats a minute), with weakness of the pulse. The heart sounds were rather muffled; the extremities were cold... Thereafter a constant symptom appeared - insomnia lasting several days... A state of giddiness persisted, accompanied by abundant sweating and a disagreeable odour. The special odour struck the patient and his attendants.

In most patients, these symptoms, including the total insomnia, persisted for several days. In some of the patients, these symptoms progressed to full-blown psychosis:

Logorrhoea [speaking a lot], psychomotor agitation, and absolute insomnia always presaged the appearance of mental disorders. Towards evening visual hallucinations appeared, recalling those of alcoholism. The particular themes were visions of animals and of flames. All these visions were fleeting and variable.

In many of the patients they were followed by dreamy delirium. The delirium seemed to be systematized, with animal hallucinations and self-accusation, and it was sometimes mystical or macabre. In some cases terrifying visions were followed by fugues, and two patients even threw themselves out of windows... Every attempt at restraint increased the agitation.

In severe cases muscular spasms appeared, recalling those of tetanus, but seeming to be less sustained and less painful... The duration of these periods of delirium was very varied. They lasted several hours in some patients, in others they still persist.

In total, about 150 people suffered some symptoms. About 25 severe cases developed the "delirium". 4 people died "in muscular spasm and in a state of cardiovascular collapse"; three of these were old and in poor health, but one was a healthy 25-year-old man.

At first, the cause was assumed to be ergotism - poisoning caused by chemicals produced by a fungus which can infect grain crops. Contaminated bread was, therefore, thought to be responsible. Ergotism produces symptoms similar to those reported at Pont St. Esprit, including hallucinations, because some of the toxins are chemically related to LSD.

However, there have been other theories. Some (including Albert Hofmann, the inventor of LSD) attribute the poisoning to pesticides containing mercury, or to the flour bleaching agent nitrogen trichloride.

More recently, journalist Hank Albarelli claimed that it was in fact a CIA experiment to test out the effects of LSD as a chemical weapon, though this is disputed. What really happened is, in other words, still a mystery.

Link: The Crazies (2010) is a movie about a remarkably similar outbreak of mass insanity in a small town.

GABBAI, LISBONNE, & POURQUIER (1951). Ergot poisoning at Pont St. Esprit. British medical journal, 2 (4732), 650-1 PMID: 14869677

Massive Magnets Reveal More Sex In the Brain

"Is that a 7 Tesla magnet in your pocket, or are you just pleased to see me?"

German neuroscientists Metzger et al report on the results of a study using the latest, ultra-high-field Magnetic Resonance Imaging to measure brain activity in response to sexually arousing stimuli.

Most fMRI studies are done using MRI scanners with a field strength of either 1.5 Tesla or, most commonly nowadays, 3.0 Tesla. However, a few especially forward-thinking, by which I mean wealthy, research centres have started investing in 7 Tesla scanners.

Stronger magnetic fields mean that the scanner is able to pick up smaller differences in brain activation, with a better temporal and spatial resolution, although it's not all good news because some of the artefacts that can spoil MRI images also get worse with higher fields. 7 Tesla magnets are also so incredibly powerful that you literally have to tread carefully around them: move too fast through the field, and you can suffer dizziness, vertigo, and visual disturbances...

Anyway, Metzger et al's paper is one of the first 7 Tesla fMRI studies and it's pretty cool. They managed to achieve a spatial resolution of 1.7 x 1.7 x 3 mm , or about three times better than most studies, and a temporal resolution of 1 second, twice or three times better than usual.

They showed heterosexual male subjects a range of pictures, some of them pornographic, others "emotional" but non-sexual. They found that anticipating seeing a picture, as opposed to than actually viewing one, activated different areas of the cortex and also of the thalamus (see image above). Sexual arousal was also correlated with activity in a third thalamic area.

This fits with previous work, so it's not too surprising, but it shows the power of 7 Tesla fMRI: as you can see, the thalamus is a small structure, and conventional fMRI struggles to localize activity to particular subdivisions of it. But we know that the thalamus is a hotbed of activity, because almost all the information that goes to and from the rest of brain passes through it. Until now, fMRI researchers have tended to treat the thalamus as a no-man's land but with any luck, 7 Tesla scanners will start to change that. For those who can afford them...

Metzger CD, Eckert U, Steiner J, Sartorius A, Buchmann JE, Stadler J, Tempelmann C, Speck O, Bogerts B, Abler B, & Walter M (2010). High field FMRI reveals thalamocortical integration of segregated cognitive and emotional processing in mediodorsal and intralaminar thalamic nuclei. Frontiers in neuroanatomy, 4 PMID: 21088699

The 9 Circles of Scientific Hell

Dante's Inferno: a classic of world literature, the definitive statement of the mediaeval Christian world-view, the first major work in the Italian language, and the basis for a violent videogame. The poem offers a tour through the nine increasingly horrible levels of Hell, in which sinners are tormented forever.

But Dante lived before the era of modern science. I thought I'd update his scheme to explain what happens to those guilty of various scientific sins, ranging from the commonplace to the shocking.

Bear in mind that Dante's Hell had a place for everyone, and it was only Christ's intervention that saved anyone from it; even "good" people went to Hell because everyone sins. But they are still sins. Likewise, very few scientists (and I'm certainly not one of them) would be able to avoid being condemned to some level of this Inferno... but, that's no excuse.

First Circle: Limbo

"The uppermost circle is not a place of punishment, so much as regret. Those who have committed no scientific sins as such, but who turned a blind eye to it, and encouraged it by their awarding of grants and publications, spend eternity on top of this barren mountain, watching the carnage below and reflecting on how they are partially responsible..."

Second Circle: Overselling
"This circle is reserved for those who exaggerated the importantance of their work in order to get grants or write better papers. Sinners are trapped in a huge pit, neck-deep in horrible sludge. Each sinner is provided with the single rung of a ladder, labelled 'The Way Out - Scientists Crack Problem of Second Circle of Hell"

Third Circle: Post-Hoc Storytelling
"Sinners condemned to this circle must constantly dodge the attacks of demons armed with bows and arrows, firing more or less at random. Every time someone is hit in some part of their body, the demon proceeds to explain at enormous length how they were aiming for that exact spot all along."

Fourth Circle: P-Value Fishing

"Those who tried every statistical test in the book until they got a p value less than 0.05 find themselves here, an enormous lake of murky water. Sinners sit on boats and must fish for their food. Fortunately, they have a huge selection of different fishing rods and nets (brandnames include Bayes, Student, Spearman and many more). Unfortunately, only one in 20 fish are edible, so they are constantly hungry."

Fifth Circle: Creative Use of Outliers
"Those who 'cleaned up' their results by excluding inconvenient data-points are condemned here. Demons pluck out their hairs one by one, every time explaining that they are better off without that hair because there was something wrong with it."

Sixth Circle: Plagiarism

"This circle is entirely empty because as soon as a sinner arrives, a winged demon carries them to another circle and forces them to suffer the punishment meted out to the people there. After their 3 year "post" is up, they are carried to another circle, and so on..."

Seventh Circle: Non-Publication of Data
"Here sinners are chained to burning chairs in front of desks covered with broken typewriters. Only if they can write an article describing their predicament, will they be set free. Each desk has a file-drawer stuffed full of these, but the drawers are locked.

Eighth Circle: Partial Publication of Data
"At any one time exactly half of the sinners here are chased around by demons prodding them with spears. The demons choose who to chase at random after ensuring that the groups are matched for age, gender, height and weight. Howling desert winds blow a constant torrent of articles announcing the success of a new program to enhance participation in physical exercise - but with no mention of the side effects."

Ninth Circle: Inventing Data
"Here Satan himself lies trapped forever in a block of solid ice alongside the worst sinners of all. Frozen in front of their eyes is a paper explaining very convincingly that water cannot freeze in the environmental conditions of this part of Hell. Unfortunately, the data were made up."

Links: This has been kindly translated into Russian here and into Portuguese here.

Autism Gives You Biblical Superpowers

We've all heard about autistic "savants" with amazing mathematical, memory or artistic abilities. But could autism give you the power to kill 1,000 men armed only with a donkey bone?

Samson was the original Chuck Norris. Granted mighty strength by God so long as he didn't cut his hair or shave, Samson's first act of heroism was ripping a lion to shreds with his bare hands. Then he moved onto people. According to the Book of Judges:

"And Samson said, With the jawbone of an ass, heaps upon heaps, with the jaw of an ass have I slain a thousand men." - Judges 15:16

Samson later bested even this achievement. Finding himself trapped in a building with over 3,000 enemies who were about to sacrifice him to their pagan god, Samson single-handedly demolished the building by smashing some pillars, killing everyone including himself.

What does this have to do with autism? Well, according to Indian neurologists Mathew and Pandian in a new paper, it shows that Samson had it. No, really.

One of the earliest incidents recorded from Samson's adult life is the journey to Timnath with his parents where he tears a lion with his bare hands. On his return, he finds a swarm of bees and honey in the carcass of the lion, which he eats, and offers his parents (Judges 14:8-9). Abnormal eating is one of the atypical behaviors noted among children with autism [ref].

Throughout Samson's life, it is seen that he performed extraordinary physical feats... It is possible that Samson was able to perform these feats as he may have been insensitive to pain, which is occasionally seen among autistics [ref]. A study of hospitalized individuals carried out in Sweden had reached the conclusion that individuals with autism or autism spectrum disorders are prone to acts of violence [ref].

Hmm. Fair to say this falls into the "speculative" category. They also diagnose other Biblical characters with various disorders ranging from strokes to acromegaly but Samson's autism is certainly the most "interesting" of the bunch.

Link: This study also blogged at Autism Jabberwocky, an extremely good blog I only found out about yesterday. I've subscribed, you should too.

Mathew SK, & Pandian JD (2010). Newer insights to the neurological diseases among biblical characters of old testament. Annals of Indian Academy of Neurology, 13 (3), 164-166 PMID: 21085524