Longitudinal neuropsychological change in first-episode schizophrenia

The presence of cognitive dysfunction is a well-documented finding in samples of chronic as well as first episode patients with schizophrenia. Questions remain as to the nature of neuropsychological dysfunction over the course of the illness. From our first episode cohort, 17 patients have repeatedly been assessed at 6, 18, and 36 months following treatment for the first episode; these represent stable periods of illness. Comprehensive neuropsychological evaluations yielded 7 domains of function: language, attention, executive function, motor, memory, visual-spatial, and global function (mean of other scales). Each domain was standardized (deviation z scores were calculated) relative to 36 healthy controls. Repeated measures MANOVA with planned contrasts (across time periods) revealed significant improvement on all measures from 6 to 18 months; no further improvement was observed on any domain from 18 to 36 months. In terms of absolute change, improvement on individual scales from 6 to 18 months ranged from 0.33 s.d. (executive function) to 0.84 s.d. (motor functioning). In terms of global neuropsychological functioning, the sample improved from −1.71 s.d. to −1.06 s.d. below control levels. Examination of test-retest correlations revealed generally high test-retest stability in the distributions over time. Degree of symptomatology remained generally stable over time; neuropsychological improvement was only mildly correlated with symptom fluctuation (negative symptom improvement). Overall, the findings reveal some normalization of cognitive function which is maximal in the 18 months following the first episode. Following improvement, the patients retain significant residual neuropsychological impairment relative to controls.