Born in Summer? Men Might Have Higher Risk of Depression

Men born during the summer months tend to report higher depression symptoms than those born in other seasons, as per a study by Kwantlen Polytechnic University. Anxiety levels were not influenced by birth season for either gender.

Depression and anxiety remain prevalent mental health disorders worldwide, leading to long-term disabilities and significant economic impacts. Various factors influence mental health across lifetimes, such as housing, income, education, and age. Research on the impact of early-life exposures is limited, especially regarding environmental seasonality.

Factors during pregnancy, like temperature shifts, maternal diet, seasonal infections, and changes in daylight, may affect brain development. Birth season has been linked to risks for conditions such as schizophrenia, bipolar disorder, and schizoaffective disorder. Previous studies on birth season's connection to depression have yielded mixed results, often without separating data by sex.

The study "Investigating the association between season of birth and symptoms of depression and anxiety in adults," published in PLOS Mental Health, analyzed whether birth seasons impact adult anxiety or depression symptoms through an online survey.

Participants (n=303) were mostly women (65%), averaging 26 years old. The study collected data online from January to March 2024, primarily in Vancouver, BC.

The participants completed a 20-minute online questionnaire that included the PHQ-9 and GAD-7 scales to assess depression and anxiety severity. Birth months were categorized by meteorological season. Researchers applied generalized linear mixed models to analyze the relationship between birth seasons and symptoms scores. Sex and birth season were fixed effects, while age, income, and interactions between month of birth and latitude served as random effects.

Depression was at notable levels in 84% of respondents, compared to anxiety's 66%. This high prevalence might reflect the sample's young, student-heavy winter population.

Across most demographic groups, depression scores exceeded typical thresholds. Summer-born men exhibited slightly higher scorers than others, whereas women displayed no significant association with birth seasons. Anxiety did not correlate with season or sex interaction.

Females showed no relationship between birth season and depression. Similarly, anxiety symptoms were unaffected by birth season in both genders.

The researchers concluded that birth season could serve as a proxy for early environmental influences on depression risk differently affecting each gender. Future studies should explore biological pathways involving photoperiod, maternal nutrition, and immune activation during pregnancy.

Study limitations include its cross-sectional nature, data collection in winter months only, absence of abiotic exposure metrics, and reliance on a convenience sample mostly consisting of students, all of which constrain causal inference and broad applicability.

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