Symptomatic remission and cognitive impairment in first-episode schizophrenia: a prospective 3-year follow-up study

Objective: Cognitive impairment is a core feature of schizophrenia, but its relationship with symptomatic remission has been understudied. This study aimed to examine the concurrent and longitudinal relationships between cognitive functioning and symptomatic remission in first-episode schizophrenia.

Method: The sample comprised 92 Chinese patients, aged 18 to 55 years, who presented with first-episode DSM-IV schizophrenia spectrum disorder and were recruited from both outpatient and inpatient psychiatric units covering a defined catchment area in Hong Kong. The study commenced in September 1997 and ended in March 2005. Psychopathological evaluation was conducted using the Positive and Negative Syndrome Scale (PANSS) and the High Royds Evaluation of Negativity (HEN) scale at intake, after clinical stabilization of the first psychotic episode, and at 12, 24, and 36 months. Cognitive functions were measured at clinical stabilization and at 12, 24, and 36 months. Sustained symptomatic remission was operationally defined as fulfillment of mild severity ratings or less at 24 and 36 months on selected PANSS items for positive symptoms and on the basis of Andreasen's criteria and HEN subscales for negative symptoms.

Results: At the end of the 3-year follow-up, 44.6% of patients achieved sustained symptomatic remission. Remitted patients had significantly better concurrent verbal memory (F = 4.6, P < .01) and functional (t = -2.4, P < .05) and vocational (t = 4.8, P < .01) outcomes at 36 months than nonremitted counterparts. Sustained remission attainment was associated with better premorbid adjustment (t = -3.1, P < .01), better baseline occupational status (χ(2) = 4.7, P < .05), better 1-year verbal memory (F = 6.4, P < .01), and fewer 1-year positive (t = -2.9, P < .01) and negative (t = -4.7, P < .01) symptoms. Logistic regression indicated that verbal memory impairment, premorbid functioning, and negative symptom severity independently predicted remission status (Nagelkerke R(2) = 0.425, P < .0001).

Conclusions: Our findings provide supportive evidence that verbal memory impairment might be specifically related to attainment of sustained remission in the early stage of schizophrenia.