As is my usual habit, I sat down tonight to do something useful and wound up flicking though Facebook instead.  Procrastination … avoidance behaviour … yeah, probably.  But at least this time it turned out to be rather useful procrastination, because I came across a science news story on Science Daily about a study linking the use of anti-depressants in pregnancy with an 87% increased risk of autism.

Actually, this is old news.  Other studies have linked the use of some anti-depressants with an increased risk of autism, such as Rai et al in 2013 [1].

The latest study to come out used data from a collaboration called the Quebec Pregnancy Cohort and studied 145,456 children between the time of their conception up to age ten.  In total, 1,045 children in that cohort were diagnosed with autism of some form, which sounds like a lot, but it was only 0.72%, which is actually lower than the currently accepted prevalence of autism in the community of 1%.

What the researchers got excited about was the risk of developing autism if the mother took an antidepressant medication at least at one time during her pregnancy.  Controlling for other variables like the age, wealth, and other health of the mothers, a woman who took an anti-depressant during pregnancy had a 1.87 times greater chance that her baby would end up with ASD, compared to women who did not take an anti-depressant [2].

An 87% increase sounds like an awful lot.  In fact, it sounds like another reason why anti-depressants should be condemned … right?

Well, like all medical research, you’ve got to consider it all in context.

First, you’ve always got to remember that correlation doesn’t always equal causation.  In this particular study, there was a large number of women being followed, and their children were followed for a long enough time to capture all of the likely diagnoses.  So that’s a strength.  They also tried to control for a large number of variable when calculating the risk of anti-depressants, which also adds more weight to the numbers.

Although the numbers are strong, studies like these can’t prove that one thing causes another, merely that they’re somehow linked.  It might be that taking anti-depressants causes the brain changes of autism in the foetus, but this sort of study can’t prove that.

Even if the relationship between anti-depressants and ASD was cause-and-effect, what’s the absolute risk?  Given the numbers in the study, probably pretty small.  With a generous assumption that ten percent of the study population was taking anti-depressants, the increase in the absolute risk of a women taking anti-depressants having a child with ASD is about 0.5%.  Or, there would be one extra case of autism for every 171 that took anti-depressants.

Hmmm … when you think of it that way, it doesn’t sound as bad.

You also have to consider the increase in risk to women and their offspring when they have depression that remains untreated, or in women that stop their anti-depressant medications.  There is some evidence that babies born to women with untreated depression are at risk of prematurity, low birth weight, and growth restriction in the womb, as well as higher impulsivity, poor social interaction, and behavioural, emotional and learning difficulties.  For the mother, pregnant women with depression are more at risk of developing postpartum depression and suicidality, as well as pregnancy complications such as preeclampsia, and an increase in high-risk health behaviour such as smoking, drug and alcohol abuse, and poor nutrition.  Women who discontinued their antidepressant therapy relapsed significantly more frequently compared with women who maintained their antidepressant use throughout pregnancy (five times the rate) [3].

So the take home messages:

1. Yes, there’s good evidence that taking anti-depressants in pregnancy is linked to an increased risk of a child developing autism.
2. But the overall risk is still small. There is one extra case of autism for every 171 women who take anti-depressants through their pregnancy.
3. And this should always be balanced out by the risks to the mother and child by not adequately treating depression through pregnancy.
4. If you are pregnant or you would like to become pregnant, and you are taking anti-depressants, do not stop them suddenly. Talk to your GP, OBGYN or psychiatrist and work out a plan that’s best for you and your baby.

References

[1]       Rai D, Lee BK, Dalman C, Golding J, Lewis G, Magnusson C. Parental depression, maternal antidepressant use during pregnancy, and risk of autism spectrum disorders: population based case-control study. Bmj 2013;346:f2059.
[2]       Boukhris T, Sheehy O, Mottron L, Bérard A. Antidepressant use during pregnancy and the risk of autism spectrum disorder in children. JAMA Pediatrics 2015:1-8.
[3]       Chan J, Natekar A, Einarson A, Koren G. Risks of untreated depression in pregnancy. Can Fam Physician 2014 Mar;60(3):242-3.