LONDON - Children exposed to antidepressants during their mothers' pregnancies seem to have a slightly higher risk of autism than children whose mothers had psychiatric disorders but did not take antidepressants while pregnant, a study has found.
But publishing their findings on Wednesday, researchers said the results should not cause alarm, since the absolute risk of a child developing autism remains very small.
Depression is common in women of childbearing age. In Europe, experts say that between 3 and 8 per cent of pregnant women are prescribed antidepressants.
Several previous studies have suggested associations between antidepressant use during pregnancy and autism in offspring, but researchers say it is not clear whether this is due to the illness itself, the antidepressants, or other unknown factors.
A Canadian study published late in 2015 found that women who take antidepressants while pregnant may be more likely to have children with autism - but it also noted that the overall risk is very low.
For this research, a team led by Dheeraj Rai at Britain's University of Bristol, analysed data from more than 254,000 children living in Stockholm, Sweden, aged between 4 and 17.
Their mothers were either women with no mental illness who had not taken antidepressants, women who'd had a disorder and taken antidepressants while pregnant, or women with psychiatric disorders who had not taken antidepressants during pregnancy.
Of the 3,342 children exposed to antidepressants during pregnancy, the study found that 4.1 per cent were diagnosed with autism, compared with 2.9 per cent of the 12,325 children not exposed to antidepressants whose mothers had a history of a mental illness.
The researchers stressed, however, that the absolute risk was small: More than 95 per cent of women in the study who took antidepressants during pregnancy did not have an autistic child.
They estimated that, even if the association between antidepressant use and autism is causal, only 2 per cent of cases would be prevented if in future no women with psychiatric disorders took antidepressants when pregnant.
In a commentary on the findings, published in the BMJ British medical journal, Diana Schendel at Denmark's Aarhus University said the findings "should be viewed through the kaleidoscope of possible causes of autism".
She said the small apparent increased risk of a child developing autism "must be carefully weighed against the substantial health consequences associated with untreated depression."