Post-psychotic depression: Paranoia and the damage done.

To mitigate the often chronic course of schizophrenia and improve functional outcome, researchers are increasingly interested in prodromal states and psychological risk factors that may predict the outbreak of psychotic symptoms, but are also amenable to change. In recent years, depressive symptoms have been proposed as precursors of psychosis and some interventional studies indicate that the amelioration of depressive symptoms and depression-related thinking styles (e.g., worrying) improves positive symptoms, thereby "killing two birds with one stone". Yet, in a prior study, we were unable to find a strong specific predictive role of depression on paranoia over three years, which may have been due to the use of a nonclinical sample with minimal/mild symptom fluctuations. To address this further, in the present study we adopted a similar methodological approach but assessed a large patient sample with a schizophrenia spectrum disorder at three assessment points; baseline (N = 250), 6 weeks later (n = 207, 82.8% retention) and 6 months after baseline (n = 185, 74% retention). Using cross-lagged modeling, we assessed paranoia with the respective items from the Positive and Negative Syndrome Scale (PANSS) and the Psychosis Rating Scales (PSYRATS) delusions subscale. Depression was measured using the Patient Health Questionnaire-9 (PHQ-9) and the Calgary Depression Scale for Schizophrenia (CDSS). We could identify a significant pathway from depression to paranoia from baseline to post (negative association) but not from post to follow-up. Paranoia significantly predicted depressive symptoms for both intervals. Our findings do not refute claims that depression may precede or even predict psychosis, but such a linkage does not seem to be ubiquitous.