Sustained attention-deficit confirmed in euthymic bipolar disorder but not in first-degree relatives of bipolar patients or euthymic unipolar depression

Background: Cognitive dysfunction persists in the euthymic phase of bipolar disorder and may provide a marker of underlying neuropathology and disease vulnerability. This study aimed to replicate a deficit in sustained attention in euthymic bipolar patients and investigate sustained attention in first-degree relatives of bipolar probands and in remitted patients with major depressive disorder. Methods: The rapid visual information processing (RVIP) task was used to measure sustained attention in 15 euthymic patients with bipolar disorder and 15 control subjects in experiment 1 and in 27 first-degree relatives of bipolar, 15 remitted patients with major depressive disorder, and 46 control subjects in experiment 2. Results: Sustained attention deficit was confirmed in the euthymic bipolar patients in experiment 1, but the deficit was not statistically significant in remitted major depressed patients or in the relatives of bipolar probands. Conclusions: A deficit of sustained attention is not present in patients with recurrent major depression tested during remission nor is it discriminable in the first-degree relatives of bipolar probands. Thus, the confirmed abnormality in euthymic bipolar patients may be acquired as a consequences of bipolar illness. However, future studies of relatives will require larger samples sizes to exclude or utilize small genetic effects.