Cross-sectional and longitudinal associations between psychotic and depressive symptoms in depressed adolescents.

Adults with major depressive disorder (MDD) with psychotic features (delusions and/or hallucinations) have more severe symptoms and a worse prognosis. Subclinical psychotic symptoms are more common in adolescents than adults. However, the effects of psychotic symptoms on outcome of depressive symptoms have not been well studied in adolescents. Depressed adolescents aged 11-17 with and without psychotic symptoms were compared on depression severity scores at baseline and at 28- or 42-week follow-up in two large UK cohorts. Psychotic symptoms were weakly associated with more severe depression at baseline in both cohorts. At follow-up, baseline psychotic symptoms were only associated with depressive symptoms in one sample; in the other, the effect size was close to zero. This supports the DSM5 system of psychotic symptoms being a separate code to severity rather than the ICD10 system which only allows the diagnosis of psychotic depression with severe depression. There was no clear support for psychotic symptoms being a baseline marker of treatment response.