Impairment of executive function but not memory in first-degree relatives of patients with bipolar I disorder and in euthymic patients with unipolar depression.

OBJECTIVE

The authors' goal was to characterize cognitive flexibility and verbal learning in relatives of patients with bipolar disorder and in euthymic patients with recurrent major depression.

METHOD

The intradimensional/extradimensional shift task and California Verbal Learning Test were administered to 27 first-degree relatives of probands with bipolar I disorder, 15 euthymic outpatients with recurrent unipolar depression, and 47 healthy comparison subjects.

RESULTS

The relatives of patients with bipolar I disorder and the euthymic patients with unipolar depression were more likely to fail the intradimensional/extradimensional shift task than the healthy comparison subjects. The impairments at the extradimensional shift stage were pronounced. Verbal learning, delayed recall, and recognition were unimpaired in all groups.

CONCLUSIONS

Attentional set shifting may represent an endophenotype in mood disorder, related to underlying vulnerability rather than the actual disease phenotype.