Babies exposed to antidepressants in the womb may have a slightly higher risk of autism than babies of mothers with psychiatric disorders who were not treated with antidepressants during pregnancy, according to a new study published in The BMJ.
The researchers stress, however, that the absolute risk of autism was small, so the findings should not be considered alarming.
While previous research has shown a link between antidepressant use during pregnancy and autism in children, it remained unclear whether this is due to the underlying illness, antidepressant medications or other factors.
Such confounding factors can introduce bias and affect the study results, making it harder for researchers to draw firm conclusions about cause and effect.
For the study, a research team at the University of Bristol in the U.K. applied a range of analytical methods to a large Swedish population.
They analyzed data from 254,610 individuals aged four to 17, including 5,378 with autism, living in Stockholm in 2001-11 who were born to mothers who did not take antidepressants and did not have any psychiatric disorder, mothers who took antidepressants during pregnancy, or mothers with psychiatric disorders who did not take antidepressants during pregnancy.
Of the 3,342 children exposed to antidepressants during pregnancy, 4.1 percent (136) had a diagnosis of autism compared with 2.9 percent (353) in 12,325 children not exposed to antidepressants whose mothers had a history of a psychiatric disorder.
No link was found between an increased risk of autism and the father’s use of antidepressants.
The findings appear to be consistent, say the authors, suggesting that the link between antidepressant use in pregnancy and autism might not be fully explained by confounding factors.
They point to some study limitations, however, such as lack of detailed measures of severity of depression. However, key strengths were the large sample size and the range of analyses carried out to minimize bias.
It is also important to note that the absolute risk was small (over 95 percent of women in the study who took antidepressants during pregnancy did not have a child with autism), stress the authors.
So even if the link between antidepressant use and autism is causal, only around 2 percent of cases would be prevented if no women with mental disorders used antidepressants during pregnancy.
They call for “a balanced discussion in relation to clinical decision-making in the light of evolving but yet inconsistent evidence” and say “it is important to continue investigation of possible underlying biological mechanisms that could help us to better understand the etiology of autism.”