Most research has found a positive association between religious belief and mental health, but these are often in US samples, which may differ from samples in other countries. We have previously examined childhood and adolescent mental health and parental religious belief, which have found results that differ from much of the previous literature. This study seeks to expand upon our previous studies of childhood and adolescent mental health by examining adult mental health, and whether offspring religious belief is associated with it in a large UK cohort study.