By Mark Cowen, Senior medwireNews Reporter

Trait impulsiveness is associated with a severe course of bipolar disorder (BD), researchers report.

Bruno Etain (Hôpital Albert Chenevier, Créteil, France) and colleagues found that higher impulsiveness scores were associated with rapid cycling, a history of mixed episodes, and substance misuse in patients with BD.

However, the team found no significant association between impulsiveness and suicidality in patients with the mood disorder.

The authors comment in the Journal of Affective Disorders that "further studies are required to clarify the role of trait-impulsiveness, particularly in high-risk populations, such as healthy first-degree relatives of bipolar patients, to explore the relevance of impulsiveness as an endophenotype of the disorder."

The findings come from a study of 385 euthymic BD patients, aged at least 18 years, and 185 mentally healthy individuals (controls).

All of the participants were assessed for impulsivity using the Barratt Impulsiveness Scale (BIS-10).

As expected, the researchers found that BD patients had significantly higher total BIS-10 scores, and significantly higher scores for all three subscales (motor, attentional, and nonplanning impulsiveness) than controls, after adjustment for age and gender.

Among the BD patients, those who misused alcohol or cannabis had significantly higher BIS-10 total scores than those who did not, at 69.40 versus 65.24, and 72.00 versus 65.29, respectively.

BD patients with a history of mixed episodes also had significantly higher BIS-10 total scores than those without, at 69.12 versus 64.95, as did those with a history of rapid cycling, at 69.81 versus 65.56.

There was no significant association between BIS-10 total score and history of suicide attempts, number of suicide attempts, age at first suicide attempt, and personal history of violent suicide attempts, the researchers note.

"This study provides additional evidence in favor of a major role of trait-impulsiveness in the more severe types of clinical expression of bipolar disorders, including substance misuse and greater mood instability, but not in suicidal behaviour," Etain et al conclude.

They add: "The codification of therapeutic interventions as a function of impulsiveness level is required. Nevertheless, such a dimension should be included in personalized medicine that is developing for bipolar patients."

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