The Relationship between Cognitive Decline and Psychopathology in Patients with Schizophrenia and Bipolar Disorder

Objective: The primary goals of the present study were to assess intellectual function in participants with schizophrenia or bipolar disorder (BD) and to investigate the relationships between cognitive decline and the severity of each type of psychopathology. Methods: The present study included 51 patients with schizophrenia and 42 with BD who were recruited from the psychiatry outpatient clinic of Jeju University Hospital between March 2011 and March 2014. The Korean Wechsler Adult Intelligence Scale (K-WAIS) was administered to each of the 93 participants, and they were categorized into two groups based on their current intelligence quotient (IQ) and their estimated premorbid IQ: severely impaired group (SIG) and mildly impaired group (MIG). The Minnesota Multiple Personality Inventory (MMPI) and the Brief Psychiatric Rating Scale (BPRS) were used to assess psychopathology. Results: The SIG schizophrenia participants exhibited significantly higher scores on the frequent (F) and schizophrenia (Sc) subscales of the MMPI, but significantly lower scores on the correction (K) and psychopathic deviate (Pd) subscales compared with the MIG schizophrenia participants. Furthermore, the BPRS scores were significantly higher in the SIG schizophrenia participants relative to the MIG schizophrenia participants. The SIG BD participants had significantly higher F, masculinity-femininity (Mf), paranoia (Pa), and Sc but significantly lower Pd scores compared with the MIG BD participants. Conclusion: The present findings revealed a significant discrepancy between the estimated premorbid levels of cognitive function and current cognitive function in participants with schizophrenia or BD. Moreover, this discrepancy was correlated with severity of psychopathology in both groups,