BackgroundPsychotic experiences (PEs) are not exclusive to psychotic disorders and highly correlated with mood episodes. In this representative general population-based study, longitudinal bidirectional associations between the extended psychosis phenotype and mood episodes were investigated, accounting for other possible causes.MethodsHouseholds were contacted in a multistage clustered probability sampling frame covering 11 districts and 302 neighbourhoods at baseline (n=4011) and at 6-year follow-up (n=2185). Participants were interviewed with the relevant sections of the composite international diagnostic interview both at baseline and at follow-up. Sociodemographic, familial and environmental risk factors associated with the extended psychosis phenotype and mood episodes were assessed. Logistic regression and cross-lagged panel correlation models were used for the associations between the extended psychosis phenotype and mood episodes.ResultsPEs were associated with subsequent depressive and manic episodes. There was bidirectionality in that mood episodes were associated with subsequent PEs, and PEs were associated with subsequent mood episodes. The associations occurred in a sub-additive pattern. There were substantial synchronous and cross-lagged correlations between these psychopathology domains, with reciprocally similar cross-lagged correlations. Familial risk and adverse life events were associated with both psychopathology domains, whereas some sociodemographic risk factors and alcohol/cannabis use were associated with only one domain.ConclusionThe sub-additive bidirectional associations between PEs and mood episodes over time and the similarity of cross-lagged correlations are suggestive of mutually causal connections between affective and psychotic domains of psychopathology.