Deconstructing sub-clinical psychosis into latent-state and trait variables over a 30-year time span.
BACKGROUND
Our aim was to deconstruct the variance underlying the expression of sub-clinical psychosis symptoms into portions associated with latent time-dependent states and time-invariant traits.


METHODS
We analyzed data of 335 subjects from the general population of Zurich, Switzerland, who had been repeatedly measured between 1979 (age 20/21) and 2008 (age 49/50). We applied two measures of sub-clinical psychosis derived from the SCL-90-R, namely schizotypal signs (STS) and schizophrenia nuclear symptoms (SNS). Variance was decomposed with latent state-trait analysis and associations with covariates were examined with generalized linear models.


RESULTS
At ages 19/20 and 49/50, the latent states underlying STS accounted for 48% and 51% of variance, whereas for SNS those estimates were 62% and 50%. Between those age classes, however, expression of sub-clinical psychosis was strongly associated with stable traits (75% and 89% of total variance in STS and SNS, respectively, at age 27/28). Latent states underlying variance in STS and SNS were particularly related to partnership problems over almost the entire observation period. STS was additionally related to employment problems, whereas drug-use was a strong predictor of states underlying both syndromes at age 19/20. The latent trait underlying expression of STS and SNS was particularly related to low sense of mastery and self-esteem and to high depressiveness.


CONCLUSIONS
Although most psychosis symptoms are transient and episodic in nature, the variability in their expression is predominantly caused by stable traits. Those time-invariant and rather consistent effects are particularly influential around age 30, whereas the occasion-specific states appear to be particularly influential at ages 20 and 50.
Department of General and Social Psychiatry, Psychiatric University Hospital, University of Zurich, Zurich, Switzerland; Collegium Helveticum, a Joint Research Institute between the University of Zurich & ETH Zurich, Switzerland. Electronic address: roessler@dgsp.uzh.ch.
Wulf
W
Rössler
Michael P
MP
Hengartner
Vladeta
V
Ajdacic-Gross
Helene
H
Haker
Jules
J
Angst
D016009:Chi-Square Distribution; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D010551:Personality; D011618:Psychotic Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology*; D012044:Regression Analysis; D011795:Surveys and Questionnaires; D013557:Switzerland; D013997:Time Factors; D055815:Young Adult
Cannabis; Epidemiology; Latent state–trait model; Schizotypal personality; Schizotypy; Sub-clinical psychosis; Substance use