The distribution of self-reported psychotic-like experiences in non-psychotic help-seeking mental health patients in the general population: a factor mixture analysis

Purpose: Factor mixture analysis (FMA) and item response mixture models in the general population have shown that the psychosis phenotype has four classes. This study attempted to replicate this finding in help-seeking people accessing mental health services for symptoms of non-psychotic mental disorders. Methods: All patients (18–35 years old) referred for nonpsychotic mental health problems to the secondary mental healthcare service in The Hague between February 2008 to February 2010 (N = 3,694), were included. Patients completed the Prodromal Questionnaire (PQ). Hybrid latent class analysis was applied to explore the number, size and symptom profiles of the classes. Results: The FMA resulted in four classes. Class 1 (N = 1,039, 28.1 %) scored high on conceptual disorganization, inattention and mood disorder. Patients in Class 2 (N = 619, 16.8 %) endorsed almost all PQ-items, were more often screened as being psychotic or at high risk of developing psychosis, without care takers noticing. In Class 3 (N = 1,747, 47.3 %) perplexity, paranoia and negative symptoms were more prevalent. Patients were more often at high risk of developing psychosis. Class 4 (N = 286, 7.7 %) represented the ‘normative’ group with low probabilities for all items. Discussion: The results support the hypothesis that a representation in four classes of psychotic-like experiences can also be applied in a help-seeking population.