Impulsivity in bipolar disorder unrelated to substance abuse

By Lucy Piper, Senior medwireNews Reporter

Trait impulsivity is elevated and neurocognitive functioning is impaired in patients with bipolar disorder irrespective of whether they have a substance abuse history, research shows.

The research team found, “perhaps surprisingly,” that patients with and without a history of substance abuse had similar levels of impulsivity and neurocognitive function.

The only distinction was a significant relationship between high trait impulsivity and impaired cognition on several tasks of processing speed and executive functioning in patients without, but not with, a substance abuse history.

This implies that “the common phenotype being expressed across groups may have unique contributing factors within groups,” comments the team, led by Katherine Burdick (Mount Sinai School of Medicine, New York, USA).

The 98 patients with bipolar disorder had significantly higher total scores on the Barrett Impulsiveness Scale (BIS), at an average of 67.2 versus 54.0 for the 95 mentally healthy participants. They also scored higher on all three of the BIS subscales – attention, motor, and non-planning.

Similarly, bipolar disorder patients had significantly impaired performances on the Iowa Gambling Task (IGT) compared with mentally healthy participants. Specifically, they tended to be less consistent, making more erratic choices.

Increased impulsivity was present in euthymic patients, supporting previous reports of it having a “trait-like persistent course,” say Burdick et al in Bipolar Disorders. And it correlated with depressive symptom severity, which was in turn associated with patients responding more readily to losses versus gains on the IGT. There was no correlation between impulsivity and mania symptom severity, however.

Given the trait-like pattern of impulsivity and some aspects of cognitive impairment, the researchers expected these variables to be related to one another, but there was no evidence of this when the entire group of bipolar disorder patients was assessed. A significant relationship was only found in those without a history of substance abuse disorder.

The team calls for further more comprehensive studies to assess the impact of substance abuse histories in terms of duration and severity as well as the specific types of substances misused.

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