Abstract
BackgroundIt is unclear whether psychotic experiences (PEs) gradually merge into states of clinical psychosis along a continuum which correspond to a dimensional classification or whether latent classes appear above a certain severity threshold which correspond better to diagnostic categories of psychosis.MethodsAnnual cross-sectional surveys, 2014–19, among Chinese undergraduates (N = 47,004) measured PEs, depression and etiological risk factors using standardized self-report instruments. We created a psychosis continuum with five levels and tested linear and extra-linear contrasts in associated etiological risk factors, before and after adjustment for depression. We carried out latent class analysis.ResultsCategorical expression of psychosis, including hallucinations and delusions, nuclear symptoms, and nuclear symptoms and depression were found at severe level 5. Etiological risk factors which impacted linearly across the continuum were more common for depression. Child maltreatment impacted extra-linearly on both psychosis and depression. Family history of psychosis impacted linearly on psychosis; male sex and urban birth impacted extra-linearly and were specific for psychosis. Four latent classes were found, but only at level 5. These corresponded to nuclear schizophrenia symptoms, nuclear schizophrenia and depressive symptoms, severe depression, and an unclassified category with moderate prevalence of PEs.ConclusionQuantitative and qualitative changes in the underlying structure of psychosis were observed at the most severe level along a psychosis continuum, where four latent classes emerged. These corresponded to existing categorical classifications but require confirmation with clinical interview. PEs are non-specific and our findings suggest some are on a continuum with depression, whilst others are on a continuum with non-affective psychosis. Differing patterns of impact from etiological risk factors across the spectrum of psychopathology determine outcome at the most severe level of these continua.
Highlights
It is unclear whether psychotic experiences (PEs) gradually merge into states of clinical psychosis along a continuum which correspond to a dimensional classification or whether latent classes appear above a certain severity threshold which correspond better to diagnostic categories of psychosis
Our study suggests that a threshold, or tipping point, exists along a spectrum of psychosis and that once a certain level of severity is reached, the nature of both psychotic and depressive symptoms and their associations with each other rapidly change their state
Clear boundaries began to emerge between PEs and depressive symptom clusters at this level of severity along a psychosis continuum but clustering of both PEs and depressive symptoms occurred and diagnostic categories were confirmed using Latent Class Analysis (LCA)
Summary
It is unclear whether psychotic experiences (PEs) gradually merge into states of clinical psychosis along a continuum which correspond to a dimensional classification or whether latent classes appear above a certain severity threshold which correspond better to diagnostic categories of psychosis. If at a threshold of severity along the continuum there is both quantitative and qualitative underlying change in psychotic symptoms with appearance of latent classes [2, 3], this would support a categorical diagnostic approach. Binbay and colleagues [2] showed that increasing levels of severity along a “spectrum”, from PEs to psychotic symptoms to clinical psychosis, were influenced by a range of predictor variables. If there was a sudden shift upwards, this was positive extra-linear discontinuity, representing dramatic sudden increase in impact of the predictor variable, with underlying quantitative and additional qualitative changes in psychotic symptoms towards the most severe end of the continuum. An association between both extralinearity and appearance of latent classes along a psychosis continuum has not yet been confirmed
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