There really might be something to the idea of summertime sadness, at least for boys. A study finds that men born in the summer are more vulnerable to developing depression than men born at other times of the year.

Researchers at the Kwantlen Polytechnic University in British Columbia, Canada, conducted the study, an international survey of adults. They found that men, but not women, were more likely to experience depression symptoms later in life if their birth occurred in the summer compared to other seasons. The findings suggest that mothers are exposed to important environmental risk factors that vary throughout the calendar year, the authors say, including levels of sunshine.

Study author Mika Mokkonen was inspired to look into this topic by the kind of question you’d get making small talk at a party.

“The initial spark of the idea for this research arose when someone asked me if I believed in horoscopes. It got me wondering if there could potentially be a biological basis for them, in terms of how a person’s birthday could be associated with physiological or mental features,” he told Gizmodo.

Doctors have long known that seasonality can affect our current mental health—the clearest example being seasonal affective disorder, a type of depression that typically emerges during the winter months (summer SAD does exist, though). But there’s only been limited research looking at a possible link between birth timing and mental health, according to Mokkonen.

Mokkonen and his team conducted an online survey of 303 adults. Participants provided basic demographic information like age and answered two questionnaires commonly used to assess a person’s level of anxiety and depression. After controlling for factors like age and income, the researchers found that summer-born men (specifically people whose biological sex was male) were noticeably more likely to report depression symptoms than men born anytime else. The team’s findings were published Wednesday in the journal PLOS Mental Health.

These sorts of studies can only show a correlation between any two things (seasonality at birth and depression in this case) and not decidedly prove that being born in the summer can shape men’s mental health. The researchers also admit they only collected survey responses over a brief two-month period in early 2024, meaning they might not have been able to capture people’s “variations in depression and anxiety scores.” And while some of the participants did come from different countries, a substantial proportion were college students. It’s fair to say this is far from a thorough or complete study.

So clearly more research is needed to replicate and expand on this preliminary finding. There’s also the unanswered and likely complex question of why being born in the summer could be specifically worse for men but not women.

Seasonality has long played a role in affecting the survival of most species, Mokkonen noted. And while people today are generally more sheltered from the harshest elements of the outside world than our hunter-gatherer ancestors were, the changing aspects of the seasons might still be enough to subtly influence us as we’re developing in the womb.

“I would say it is possibly related to the environmental conditions of the mother during pregnancy,” Mokkonen said. “Consider conditions like temperature and sunlight—how do those conditions vary across the year?”

The researchers plan to continue investigating how other maternal factors, including the mother’s diet and circulating hormone levels, can affect the later health of their children. Mokkonen also points out that regardless of the season they were born in, a majority of the people in their study reported having at least some symptoms of anxiety (66%) and depression (84%). In other words, while the seasons may hold some sway over us, some things are unfortunately common across the board.