Autistic fish: the anatomy of a (potential) health scare

Some fish

“Antidepressants in water may cause autism”, said a headline on the New Scientist website this morning.

It’s an alarming thought. But those of us with a longish memory may shudder a little at the sight of the article, because it may remind us of health scares gone by.

The New Scientist article is, I should hasten to add, entirely sensible. It’s reporting on a study which found that trace amounts of certain psychiatric drugs – specifically, carbemazapine, an anti-epileptic, and fluoxetine and venlafaxine, two selective serotonin uptake inhibitor (SSRI) antidepressants – caused certain genes to alter their activity in fish. The genes in question included 324 which are associated with autism in humans. They also found that the fish exposed to the drugs were more likely than control fish to panic when startled. But, obviously, it’s a long way from there to thinking that antidepressants cause autism, and even further to the idea that the trace quantities of these psychiatric drugs which may make their way into our water supplies might increase the risk of autism.

The trouble is that this story is almost the Platonic ideal of the scientific scare story. Autism scares us, understandably: the idea of having a child who doesn’t relate to his or her parents, who cannot return our love in the way we hope, is deeply unsettling. There’s a cruel arbitrariness to it as well, and parents, in their desperate search for reasons for the unreasoned, may latch on to any explanation. Hence the MMR hoax, the zombie health scare which simply will not die: despite vast amounts of evidence showing that there is no link between autism and vaccination, a hard core of believers simply will not be convinced otherwise. The coincidence of the jab being followed by the onset of noticeable symptoms was just too great.

Similarly, the poison-in-the-tap water trope is well worn. Fluoride in our tap water has been recently been accused of causing bone growth abnormalities, arthritic pains, hormonal problems with the thyroid gland, and osteosarcoma (a form of bone cancer), all without convincing evidence. (People in the 1950s and 1960s in America thought it was a Communist plot, as well, in a marvellously Dr Strangelovesque twist.) Waste drugs in the system is not a ridiculous thing to worry about, incidentally: 15 years ago a study found that trace quantities of oestrogens which reached river water through sewage caused sex changes in fish, although to my knowledge there is no evidence of any risk to humans.

And antidepressants, and depression in general, are a hugely emotive topic. Sufferers of this crippling disease get understandably angry about articles suggesting that they should just get over it, or that it’s a fashionable first-world problem. When antidepressants themselves were found by one study to be no more effective than placebo in mild to moderate depression two or three years ago, it caused a media storm; yesterday, a similar study suggesting (with significant caveats) that exercise may not be effective either raised hackles as well. Individual sufferers have their own ways of dealing with their condition; I wonder if any suggestion that their way may not be effective could feel tantamount to implying that their disease is somehow imaginary.

So this fish-autism-antidepressants story has the feel of a ticking time-bomb. It only takes one pressure group to issue a press release and we could be looking at a panic about antidepressant drugs contaminating our water supplies and causing an autism epidemic, which could in turn anger depression sufferers who feel they’re under attack simply for taking the drugs which allow them to function.

I thought, then, that I’d get out ahead of this one. The study has shown that the drugs affect the expression of genes in fish, and that the fish may behave differently afterwards. This is not the same as “drugs cause autism in fish”. Even if it were the same as “drugs cause autism in fish”, it is not the same as “drugs cause autism in humans”, and even if that were the same, it would not be the same as “the trace amounts of drugs in drinking water can cause autism in humans”.

Interestingly, as the New Scientist mentions in its piece, there has been another study suggesting that women who take SSRIs during pregnancy are more likely to have autistic-spectrum-disorder-suffering children than women who do not: about one in 50 compared to one in 100. That’s a significant increase and worth being aware of, even though the study admits it doesn’t take into account possible third factors, such as whether mental health disorders like depression are themselves risk factors for ASD. But there is a huge, huge difference in dose between taking a drug yourself while pregnant, and drinking water that has been taken out of a river into which has flowed the treated products of a sewage plant that has contained the urine of a woman who took that same drug a few weeks ago. “The dose makes the poison”, as the saying goes. Even water kills you if you take too much of it. I don’t want to tell you that there is literally nothing to worry about, but I do strongly recommend you to put off any worrying for a few years until studies have been carried out on humans.

I was pleased to see, incidentally, that the New Scientist has since changed its headline, to the less alarming “Antidepressants in water trigger autism genes in fish”. The media has, I think, learned the lessons of MMR rather well.


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