Background: The purpose of this historical prospective study was to follow the cognitive impairment in schizophrenia from the premorbid period until shortly after the onset of the first psychotic episode within the same subjects.
Methods: Forty-four first episode schizophrenia patients were enrolled in the study. Their cognitive performance was assessed as part of the Israeli Draft Board aptitude assessments at ages 16-17, when all were found to be in good mental health (first assessment) and again, following the manifestation of the first psychotic episode (second assessment). Forty-four healthy comparisons were also enrolled and tested twice, at the same ages as the patients. Both times, the assessments included four subtests assessing abstract reasoning (Raven Progressive Matrices-R), mental speed and concentration (Otis-R), verbal reasoning (Similarities-R), and mathematical abilities (Arithmetic-R).
Results: A within group analysis did not reveal statistically significant changes between the first and the second assessment among the schizophrenia patients on any measure. However, a between group comparison of changes showed that relative to the healthy comparisons, schizophrenia patients deteriorated on the RPM-R (p=0.021) and Otis-R (p<0.001), but not on the Similarities-R and Arithmetic-R. Schizophrenia patients performed worse than comparisons in all four subtests on the first and second assessments (all p<0.01).
Conclusions: The results indicate that most of the cognitive impairment exhibited by first-episode schizophrenia patients precedes the first psychotic episode. A decline between ages 16 and 17 and the onset of psychosis is evident in some but not all cognitive functions.