Research reportImpulsivity and phase of illness in bipolar disorder
Introduction
Impulsivity is a prominent aspect of bipolar disorder. It is difficult to meet criteria for a manic episode without impulsive behavior (American Psychiatric Association, 1995). Impulsivity contributes to many of the complications of bipolar disorder, including suicide (Fawcett et al., 1997, Hudson et al., 1998) and substance abuse (Allen et al., 1998) as well as the complications of manic episodes. Bipolar disorder may be physiologically and clinically related to a range of other conditions that are characterized by impulsivity (Henry et al., 2001, McElroy et al., 1996, Moeller et al., 2001). There is, however, little information about quantitative relationships between impulsivity and the course of illness in bipolar disorder.
We have reported that patients with bipolar disorder who were not experiencing active episodes of illness had higher scores than matched controls on the Barratt Impulsiveness Scale (BIS), but did not differ on impulsive responses in the Immediate Memory Task-Delayed Memory Task (IMT-DMT), a modification of the Continuous Performance Task that provides a measure of impulsivity (Swann et al., 2001). Impulsive responses on the IMT-DMT correlated, however, with subsyndromal manic symptoms. This suggested that performance impulsivity might be sensitive to state in bipolar disorder, while impulsivity as measured by the BIS might be a more trait-related measure. Based on this possibility, we have carried out an investigation of impulsivity in manic episodes of bipolar disorder, compared to euthymic subjects and controls.
Section snippets
Methods
Subjects with bipolar disorder were inpatients at the Harris County Psychiatric Center (HCPC), a state-funded hospital operated by the Department of Psychiatry, University of Texas Medical School at Houston, or from the outpatient clinic of the University of Texas Mental Sciences Institute (UTMSI). Controls were recruited from advertisements as part of an ongoing program linked to studies of impulsivity and related disorders. There were 35 controls (18 women and 17 men), aged 35±10 years, and
BIS scores
As shown in Table 1, BIS scores were elevated in both euthymic and manic subjects with bipolar disorder compared to controls. All three components of the BIS were elevated. BIS scores of manic and euthymic subjects with bipolar disorder were essentially identical.
IMT-DMT performance
Table 2 shows that IMT commission errors were identical in euthymic subjects with bipolar disorder and controls, but were elevated in manic subjects. Correct detections were slightly reduced in manic and euthymic subjects. Table 3
Discussion
These data suggest that measures of impulsivity relate differentially to phase of illness in bipolar disorder. The BIS score appeared similarly elevated regardless of the phase of illness, whereas commission errors on the IMT-DMT were only elevated during mania. This suggests that impulsivity in bipolar disorder has state and trait related aspects. The type of impulsivity reflected by commission errors may be related to noradrenergic function (Arnsten et al., 1999, Cole and Robbins, 1989),
Acknowledgments
This work was supported by grants DA 12345 (D.M.D.), DA 08425 (F.G.M.), and the Rutherford Chair in Psychiatry (A.C.S.). We thank Glen Colton, Mary Pham, Saba Abutaseh, and the nursing staff of Unit 3E, HCPC for their valuable roles in this study.
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