MedWire News: Individuals with bipolar disorder and antisocial personality disorder (ASPD) have increased impulsivity, but the two conditions do not act synergistically to increase further impulsivity, the results of a US study indicate.

It is known that bipolar disorder and cluster B personality disorders, including ASPD, share impulsivity as a trait, but there have been few comparisons of impulsivity and its consequences between the two conditions.

Alan Swann and colleagues from the University of Texas Health Science Center in Houston therefore used the Change version of the Schedule for Affective Disorders and Schizophrenia (SADS-C) and the Barratt Impulsiveness Scale (BIS-11), among other measures, to assess 34 ASPD patients, 61 bipolar disorder patients, 24 patients with APSD and bipolar disorder, and 78 healthy controls.

Scores on the SADS-C demonstrated that patients with bipolar disorder and ASPD had greater depression and psychosis than patients with bipolar disorder alone, the team reports in the journal Acta Psychiatrica Scandinavica.

BIS-11 scores were substantially higher in patients with bipolar disorder than in controls, at an effect size of 1.45. While BIS-11 scores were significantly higher in ASPD patients than in controls, the effect size was smaller, at 0.75.

Patients with bipolar disorder and ASPD had higher BIS-11 scores than patients with ASPD alone, at an effect size of 0.75, but not higher than patients with bipolar disorder alone. BIS-11 scores were associated with conviction for crimes but there was no interaction between impulsivity and the severity of crime, the researchers note.

The co-existence of bipolar disorder with APSD increased the likelihood of substance-related comorbidities, at 20 of 33 ASPD patients without bipolar disorder versus 22 of 24 patients with both bipolar disorder and ASPD. Patients with both conditions were also more likely to attempt suicide than patients with ASPD alone, at 17 of 26 patients versus one of 26 patients.

“These data support other evidence that aspects of cluster B disorders, including but not limited to impulsivity, are related to severity of bipolar disorder,” the researchers conclude.

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