The Maudsley Bipolar Disorder Project: The Effect of Medication, Family History, and Duration of Illness on IQ and Memory in Bipolar I Disorder

Background: Despite the growing recognition of the importance of cognitive impairment in psychiatric disorders, the effect of clinical factors, such as medication use and family history of affective disorders, on cognition in bipolar I disorder patients still remains unclear. This study examines the contribution of known and potential predictors to both general intellectual function and memory in a representative population of bipolar I disorder patients.

Method: Of the 425 patients receiving treatment within a defined catchment area, 63 were identified as having bipolar I disorder. Of these patients, 43 were enrolled in the study and participated in a personal interview by a psychiatrist. All patients were invited to participate in a personal interview by a psychiatrist, and information on family history, past psychiatric history, past and current treatments, duration of illness, and age at onset was collected, in addition to demographic data. Cognitive performance was assessed using the Wechsler Adult Intelligence Scale-Revised, the National Adult Reading Test, and the Wechsler Memory Test III.

Results: Forty-three patients with DSM-IV bipolar I disorder were enrolled into the Maudsley Bipolar Disorder Project. Patients on treatment with antipsychotic drugs had a lower current full scale IQ, lower general memory scores, and lower working memory scores. A family history of affective disorders was associated with a higher full scale IQ, but not with either general or working memory measures. Duration of illness was negatively associated with general memory scores, but had no effect on either IQ or working memory measures.

Conclusion: Current antipsychotic medication, duration of illness, and family history of affective disorder were the most significant predictors of IQ and memory function in bipolar I disorder patients.