Cognitive impairment in remission in bipolar affective disorder
Background. Although the traditional view of bipolar affective disorder is that the majority of patients have full remission between episodes, recent evidence suggests that residual cognitive deficits are present. The aim of this study was to determine whether memory and executive deficits were present in a well-defined clinically remitted group of patients.
Methods. This was a case–control study of bipolar patients in remission (N = 18). Subjects had to fulfil stringent clinical criteria for inclusion into the study and had to have been in remission for at least 4 months. Subjects also had no history of substance dependence. The cognitive battery examined memory and executive function.
Results. Patients in excellent clinical remission and who reported good social adaptation showed impairment on tests of visuospatial recognition memory. Accuracy on four tests of executive function was not impaired in patients in remission compared with controls, although response latency on these executive tests was still impaired.
Conclusions. As our group and others have shown, patients with mania and unipolar depression show generalized impairment on tests of memory and executive function. In comparison, this study has demonstrated that patients in remission show a relatively specific impairment in memory with recovery of accuracy measures on executive function task. The increased response latency on the executive tasks suggests a possible small residual impairment. These findings suggest that in neuroanatomical terms, more posterior cortical function (temporal lobe) has not improved but there is at least some recovery of frontal lobe function in remission.
c1 Address for correspondence: Dr B. J. Sahakian, Department of Psychiatry, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital (Box 189), Cambridge CB2 2QQ.