Characterizing impulsivity in mania

Authors


  • In addition to the NIMH funding that supported this work directly, one or more of the investigators have received grant support to the University of Cincinnati Academic Health Center in the past year for other projects from Abbott Laboratories, AstraZeneca, Eli Lilly & Co., Esai, Forest, GlaxoSmithKline, Jazz, Orexigen, Ortho-McNeil, Sanofi-Synthelabo, Somaxon, Johnson & Johnson, Shire, Janssen, Pfizer, Bristol-Myers Squibb, Repligen, Martek, Somerset, Takeda, NIDA, NIAAA, NARSAD, the Thrasher Foundation, and the Stanley Medical Research Institute.

  • Although not directly related to any of the results, the authors note that, in the past year, the following investigators have received honoraria for speaking or consulting: SMS—Pfizer (Kendle), Eli Lilly & Co., Tikvah, France Foundation (CME company), and DiMedix (CME company); MPD—Bristol-Myers Squibb, AstraZeneca, France Foundation, GlaxoSmithKline, Eli Lilly & Co., Kappa Clinical, NIDA, and Pfizer; CMA—AstraZeneca; SLM—Abbott, AstraZeneca, Eli Lilly & Co., GlaxoSmithKline, Janssen, Jazz, OrthoMcNeil, and Wyeth-Ayerst; PEK—AstraZeneca, Eli Lilly & Co., Pfizer, Forest, and Organon. DEF, PKS, QM, MAC, RK and SA have no conflicts of interest to report.

Stephen M. Strakowski, MD, Center for Imaging Research, University of Cincinnati College of Medicine, 231 Albert Sabin Way (ML0583), Cincinnati, OH, 45267-0583, USA. Fax: +1-513-558-0187; e-mail: stephen.strakowski@uc.edu

Abstract

Objective:  To determine whether specific aspects of impulsivity (response disinhibition, inability to delay gratification, inattention) differ between healthy and bipolar manic subjects, and whether these aspects of impulsivity were associated with each other and severity of affective symptoms.

Methods:  Performance of 70 bipolar I manic or mixed patients was compared to that of 34 healthy subjects on three tasks specifically designed to study response inhibition, ability to delay gratification, and attention; namely, a stop signal task, a delayed reward task, and a continuous performance task, respectively. Correlations among tasks and with symptom ratings were also performed.

Results:  Bipolar subjects demonstrated significant deficits on all three tasks as compared to healthy subjects. Performance on the three tasks was largely independent. Task performance was not significantly associated with the severity of affective symptom ratings. However, measures of response inhibition and attention were sensitive to medication effects. Differences in the delayed reward task were independent of medication effects or symptom ratings. During the delayed reward task, although bipolar patients made their choices more slowly than healthy subjects, they were significantly more likely to choose a smaller, but more quickly obtained reward. Moreover, performance on this task was not associated with performance on the other impulsivity measures. Manic patients showed more impulsive responding than mixed patients.

Conclusions:  Bipolar I manic patients demonstrate deficits on tests of various aspects of impulsivity as compared to healthy subjects. Some of these differences between groups may be mediated by medication effects. Findings suggested that inability to delay gratification (i.e., delayed reward task) was not simply a result of the speed of decision making or inattention, but rather that it reflected differences between bipolar and healthy subjects in the valuation of reward relative to delay.

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