By Emily Reynolds
A new study has cast doubt on historic research suggesting that the season or month of someone’s birth is associated with an increased risk of certain mental health conditions.
The paper, published in Scientific Reports, looks at symptoms of anxiety and depression among more than 70,000 older adults in Europe. And it finds that there is no relationship between when they were born and the likelihood that they experience anxiety or depression.
A number of past studies have found a link between season of birth and mental health diagnoses: research has linked bipolar disorder and schizophrenia with birth month, for example. Researchers have suggested that such links could arise from nutrient intake and disease exposure varying across the course of the year. However, evidence has been mixed and more recent studies have suggested that confounding factors, particularly socioeconomic background, has more to do with these diagnoses than month of birth.
To see whether season of birth does make a difference to mental health, the team used data from a survey of 72,370 older adults from across Europe, who had been asked questions on their health. Information gathered for this study included their month and season of birth (winter, spring, summer or autumn), and the extent to which they experienced symptoms of depression or anxiety.
Overall, there was no significant relationship between participants’ month of birth and symptoms of depression or anxiety. There was some variability in some countries — for example in Hungary and Poland, depressive symptoms fluctuated a little depending on birth month, and in the Czech Republic the same was true of anxiety symptoms — but, on the whole, there was no systematic pattern.
The team also compared younger and older participants (below and above the ages of 65), male and female participants, and those from different regions of Europe. And again, there was no meaningful effect of month of birth, regardless of how participants were split up.
As noted, previous research had suggested that season of birth had a strong association with mental health. This has largely been attributed to the impact of climate, differences in sunlight and vitamin D exposure, nutrition and other factors. The team suggests that an improvement in access to healthy food — and an understanding of the nutrients pregnant women and children need — may therefore be able to explain why there was no link between month of birth and mental health symptoms in this study.
The study, therefore, indicates that season of birth may not be a good predictor of mental health later in life. However, the social and environmental factors that potentially drove the links previously found between season of birth and mental health, such as nutrition and maternal health, are still worth considering when it comes to the physical and mental health of whole families.
Emily Reynolds is a staff writer at BPS Research Digest