Can the season in which you’re born actually impact your overall mental state? A new study indicates it can.

Sreeram Ramagopalan, an epidemiologist at Queen Mary University of London, and his colleagues analyzed 58,000 British citizens with schizophrenia, bipolar disorder and recurrent depression, and 29 million people from the country’s general population. And what they found may surprise you.

Schizophrenia and bipolar disorder had statistically significant peaks among people born in January, while those with July, August and September birthdays had the lowest occurrences. In addition, depression was worse among those born in May and least significant in November babies.

Some experts blame a lack of vitamin D — often acquired from sunlight — during the latter months of pregnancy, and others say kids born late in the year may be relatively immature compared with older classmates, which could cause them to suffer academically and socially and lead to higher mental stress.

“The major implication is that once we understand the cause of these effects, then we can intervene in terms of disease prevention,” Ramagopalan said.

[LiveScience]