Causes of condition are never this simple

Whatever this study shows, it has not proven that antidepressants taken in the later months of pregnancy cause autism in children. The link between the two is strong, but there may be other factors that can explain the association, namely a common genetic predisposition to both depression in mothers and autism in their children, which has nothing to do directly with taking antidepressant drugs.

Ever since Andrew Wakefield wrongly suggested a causal link between the MMR vaccine and autism, medical researchers have been wary of anything purporting to explain the origins of this childhood condition with statistical associations.

If one thing is clear, the causes of autism are not simple. There may be a logical connection between antidepressants known as selective serotonin re-uptake inhibitors (SSRIs) taken during the critical phase of foetal brain development in the womb, and autism spectrum disorder diagnosis, as the scientists from Montreal have suggested. However, this study falls well short of proving that cause and effect.

One of the study’s problems is that is it purely observational, which means it looked at data collected in the past and then used the information to make statistical associations. A better approach, for example, would have been to use each woman as their own experimental “control” to compare the risk of autism in two different pregnancies in the same person. But that would have required a bigger study with very different methodology.

Although the statistical association between SSRIs taken in the later months of pregnancy and autism is strong, it is nevertheless a relatively small risk. Doctors will now have to balance this small increased risk in autism with the increased risk of adverse effects, including suicide, in a woman taken off her medication. This is why any woman concerned about these findings should speak to her doctor.