Religious switching and mental disorders in young adulthood: Evidence from Finnish population register data

This is the first study to analyse the interrelation between religious switching and sickness absence (SA) due to mental disorders using population register data with detailed ICD-codes. We performed a prospective cohort study based on the entire population born in Finland in 1986–2003 (N=1,060,280). Each person was observed from age 18 in 2004–2023. Cox proportional hazards models with and without sibling fixed effects, and logistic regression models that conditioned on that individuals switched religion, were applied. Differences in SA receipt due to mental disorders by religious affiliation were substantial. We observed a 44% higher hazard of SA receipt of non-affiliated individuals, and a 27% higher hazard for those with any other religion, as compared to the majority group of Lutherans at a time point when they had not switched religion. Religious switching was associated with a 38-118% higher hazard of SA receipt, depending on the type of switch. Results from models with and without sibling fixed effects were similar. The conditional logistic regression models revealed that, for most types of switching, the increase in mental health-related SA receipt was steeper before the switch as compared to after the switch. However, the incidence of mental health problems remained elevated after religious switching. These findings suggest that religious switching and poor mental health are strongly interrelated, and that the direction of causality may run in both directions.