A new study from Japan suggests that mothers experiencing extreme stress during or after pregnancy may increase their children's risk of developing autism. Researchers at Tohoku University found that children of women with perinatal depression – defined as psychological distress around the time of pregnancy – were more likely to exhibit autistic traits. This effect was observed more strongly in girls, who also tended to be born underweight and showed weaker bonds with their mothers. However, the study also noted that boys displayed significantly more autistic-like traits than girls, irrespective of their mother's mental status.

The scientists emphasized the critical importance of early identification of mothers with perinatal depression to potentially reduce the risk of autism. Their findings were based on an analysis of medical data from over 23,000 mother-child pairs, where depressive symptoms were assessed during early and mid-pregnancy, and one month postpartum. These results underscore the need for supporting maternal mental health starting in pregnancy to help mitigate adverse developmental outcomes in children, especially girls.

To delve into the biological mechanisms behind these observations, the research team developed a stress model in mice. Pregnant mice were subjected to elevated stress levels, leading them to show signs of depression and exhibit less caring maternal behaviors. Notably, their female offspring displayed autism-like behavioral patterns, including increased self-grooming and reduced social awareness. Further tests revealed that stressed mouse mothers had lower levels of oxytocin, often referred to as the 'love hormone', in a specific brain region. Correspondingly, their female offspring had fewer receptors for this hormone in the same brain area, which inhibited mother-infant bonding.

Publishing their findings in the journal Molecular Psychiatry, the researchers stated that 'Developmental delays appear to be more common in girls with autism spectrum disorder. These preliminary observations underscore the importance of screening and supporting maternal mental health.' Despite these insights, the researchers acknowledged certain limitations in their study, including a relatively small sample size and an inability to account for cultural differences.

This research builds upon previous studies, such as a paper in the British Medical Journal, which highlighted a link between antidepressant use during pregnancy and autism. That study, involving over 140,000 pregnant women, found that taking antidepressant tablets in the second and third trimesters to treat depression nearly doubled the risk of children developing the spectrum disorder. The NHS advises that some mood changes are normal during pregnancy, but antenatal depression is not uncommon, with signs including persistent sadness, irritability, changes in eating habits, negative thoughts about the baby, and difficulty concentrating or making decisions.

The discussion around autism is further informed by new research indicating that girls may be just as likely to be autistic as boys but are less likely to receive a diagnosis during childhood. Dr. Caroline Fyfe, lead author of that study, suggested that 'Our findings suggest that the gender difference in autism prevalence is much lower than previously thought, due to women and girls being underdiagnosed or diagnosed late.' Experts have deemed these findings 'timely' and 'important', lending support to the theory of significant underdiagnosis in women.

These developments occur amidst broader concerns, including Wes Streeting's call for an independent review into the surging demand for mental health, ADHD, and autism services, following warnings of potential 'over diagnosis' of these conditions. Figures from March last year indicate approximately 91,000 people aged 10 to 25 years old are awaiting referral. Some experts attribute the increasing diagnoses to growing awareness of autism spectrum disorder, which has only become widely recognized as its own condition this century.