The influence of manic episodes on grey matter volumes and general intellectual functioning in bipolar I patients.

Abstract

Objective: This study focused on the effects of manic episodes on total brain and grey matter volumes and general intelligence (IQ) in patients with a bipolar type I disorder (BPI). Volumetric reductions of the total brain and grey matter have been observed in patients with BPI. In addition, cognitive impairments are found to persevere in a euthymic state, which implicates enduring poorer cognitive functioning after mood episodes. The severity of the illness, including the number of mood episodes, has been related to these structural and cognitive impairments. The precise relation of manic episodes on neuroanatomical changes and change in cognitive functioning remains inconclusive, and will therefore be examined in this study. Methods: A total of 64 euthymic patients diagnosed with BPI and 45 healthy control subjects participated in this study. The BPI diagnosis and the euthymic state were verified using the Structured Clinical Interview for DSM-IV disorders (SCID-I). Participants completed a number of questionnaires, a structured interview, and five neuropsychological tasks. Of the participants, 62 patients and 16 control subjects participated in the magnetic resonance imaging (MRI) follow-up appointment, which included a number of structural scans. Results: Patients had smaller total brain volumes than control participants, but similar grey matter volumes. No relation between grey matter volumes and general IQ was found. However, patients had a lower general IQ compared to controls participants, whilst the groups did not differ in premorbid IQ. Furthermore, patients who experienced multiple manic episodes showed a larger decrease in general IQ compared to patients who experienced a single manic episode. Conclusions: This study indicates that manic episodes have a specific negative effect on total brain volumes and general IQ. Since the level of general IQ has been related to the functional outcome of the disorder, a higher number of manic episodes can have a negative effect on the psychosocial level of functioning and the quality of life of patients. Future research should therefore continue to investigate the effects of manic episodes on a structural as well as a functional level.