Religion and mental health in young adulthood – a register based study on differences by religious affiliation in sickness absence due to mental disorders in Finland

Background: Religiosity and spirituality are known to be positively correlated with health. This is the first study to analyse the interrelation between religious denomination and sickness absence due to mental disorders using population register data with detailed ICD-codes. A follow-up study was based on the entire population born in Finland in 1984–1996 (N=794,476). Each person was observed from age 20 in the period 2004–2018. Cox proportional hazards models were applied to analyse the association between religious denomination and first-time sickness allowance receipt from any cause and mental disorder. Mental disorders were further divided into severe mental illness (F20-F31), depression (F32- F33), anxiety (F40-F48), and any other mental disorder (all other F codes). Men and women were analysed separately. Differences in sickness absence due to mental disorders by religious affiliation were substantial. As compared to members of the Evangelical Lutheran state church, the hazard for non-affiliated women was 1.34 (95% CI: 1.30-1.39), while that for women with any other religion was 1.27 (1.19-1.35), after adjusting for own and parental characteristics. Corresponding numbers for men were 1.45 (1.39-1.50) and 1.42 (1.30-1.54), respectively. The gradient was larger for severe mental illness and depression than for anxiety and other mental disorders. For sickness absence due to any cause there was no difference between Lutherans, non-affiliated, and those with any other religion. The strong association between mental disorders and church membership as measured from administrative registers should be further examined by epidemiologists and public health practitioners.