Does normal developmental expression of psychosis combine with environmental risk to cause persistence of psychosis? A psychosis proneness–persistence model
Psychological Medicine April 1, 2007 Audrey Cougnard, Machteld Marcelis, Inez Myin-Germeys et al.
Psychotic experiences (like mild hallucinations or delusions) are common and often temporary in the general population. This study tested whether they become abnormally persistent when combined with environmental factors such as cannabis use, childhood trauma, and urban living. Using two large Dutch and German population samples, the authors found that persistence rates were low overall (26% and 31%) but increased progressively with more environmental exposures. Among those exposed to both environmental risks and baseline psychotic experiences, 21%-83% (Dutch sample) and 29%-51% (German sample) had persistent symptoms due to the synergistic interaction of these factors. The authors argue that environmental risks combine additively and synergistically with non-clinical psychotic experiences to drive persistence and eventual need for care.