Is there an association between ABO blood types and depressive symptoms among Japanese healthcare workers during the COVID-19 pandemic?

ABO blood types could be a biological predisposition for depression. The present cross-sectional analysis was conducted amid the second wave of COVID-19 in Japan during July 2020. We wanted to investigate the association between ABO blood types and depressive symptoms among workers (352 men and 864 women, aged 21-73 years) of a medical institution in Tokyo, Japan, which took a leading role in the response to COVID-19 in the country. A Poisson regression model with a robust variance estimator was used to estimate the prevalence ratio (PR) and 95% confidence interval (CI) for depressive symptoms associated with ABO blood types. Overall, the prevalence of depressive symptoms (using two questions employed from a Two-question case-finding instrument) was 22.0%. The adjusted PRs (95% CI) for depressive symptoms, comparing the carriers of blood type O, A, and AB with those of type B, were 0.88 (0.66, 1.18), 0.81 (0.62, 1.07), and 1.07 (0.74, 1.53), respectively. There was no difference in the prevalence of depressive symptoms between non-B and B carriers. The present study did not support the association of ABO blood types with depressive symptoms.