Recent studies have shown that the month you are born in can impact your mental health. Especially, the babies born in winter season. During winter and autumn months mothers have higher levels of stress hormone.
The study was first of its kind. It compared the cortisol levels in mothers during later months of gestation period. There was found to be a link between chances of developing anxiety in later periods of life and cortisol levels in mother. The study was published in Psychoneuroendocrinology. The study was conducted on 316 Caucasian women. The study found a link between environmental exposure and critical periods of fetal development. These changes in fetus could even persist in later periods of life.
The higher cortisol levels in winters during later phase of pregnancy could result in many psychiatric disorders. Although there is no hard link between winter season and stress hormone levels in women, some women could in fact experience stress levels higher in summer seasons.
Cortisol is a hormone which is secreted by adrenal gland. It is popularly called as stress hormone. Other conditions that can elevate the cortisol levels are alcoholism, depression and some health conditions. However the study showed that winter born babies are exposed to relatively higher levels of cortisol.
Data showed that salivary cortisol levels increase in winter seasons. However a 2015 study noted higher cortisol levels in summer instead on winters. The 2015 study took cortisol levels from hair instead of saliva. Hair cortisol levels can be impacted by various other factors which are not in case of saliva. But the seasonal factor impact the salivary cortisol levels most. Therefore salivary cortisol levels are more significant. For instance it was found that schizophrenia was found to be more frequently diagnosed in people born in January and February.
However there are some limitations of the study, sample size of just 316 women is too small. Also, non-Caucasian women were not considered in the study. This could raise concerns regarding extending study result to other ethnicity.
Garay, S. M., et al. (2019). Seasonal variation in salivary cortisol but not symptoms of depression and trait anxiety in pregnant women undergoing an elective caesarean section. Psychoneuroendocrinology. https://doi.org/10.1016/j.psyneuen.2019.05.029