We study the predictive power and associations of several psychological scales with respect to hospitalisations due to schizophrenic psychoses.

Temperament and Character Inventory, Physical Anhedonia Scale, Social Anhedonia Scale, Perceptual Aberration Scale, Hypomanic Personality Scale, Bipolar II Scale, and Schizoidia Scale were included in the 31-year follow-up survey of the prospective Northern Finland 1966 Birth Cohort (N=4,926). We compared subjects without any previous hospitalisations to those with previous hospital diagnoses (concurrent validity) and to those who in the eight year long follow-up were hospitalised due to schizophrenic psychosis (predictive validity). We also compared the subjects with schizophrenic psychoses and subjects with other psychiatric disorders (discriminant validity).

In most scales, subjects with schizophrenic psychoses differed from healthy subjects. The Perceptual Aberration Scale was the best scales for concurrent (Effect Size, d = 1.89) and discriminant validity (d = 0.64). Subjects having a high score in Hypomanic Personality Scale were in the highest risk for schizophrenic psychoses (OR 10.72; 95% CI 2.87-40.06).

Subjects with schizophrenic psychoses differed in most of the scales from healthy controls and from subjects with other psychiatric disorders. Many of the scales were useful predictors for future hospitalisations due to schizophrenic psychoses; however scales were not very diagnosis specific. The predictive power of the scales is limited, these scales are probably not useful as screening instruments but can be used in several ways when studying e.g. risk factors or genetics of schizophrenic psychoses.