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. 2009 Aug;43(12):1057-63.
doi: 10.1016/j.jpsychires.2009.03.003. Epub 2009 Apr 5.

Trait Impulsivity and Response Inhibition in Antisocial Personality Disorder

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Trait Impulsivity and Response Inhibition in Antisocial Personality Disorder

Alan C Swann et al. J Psychiatr Res. .
Free PMC article

Abstract

Background: Impulsive behavior is a prominent characteristic of antisocial personality disorder. Impulsivity is a complex construct, however, representing distinct domains of cognition and action. Leading models refer to impulsivity as an inability to evaluate a stimulus fully before responding to it (rapid-response impulsivity), and as an inability to delay responding despite a larger reward (reward-delay impulsivity). We investigated these models in terms of the diagnosis and severity of antisocial personality disorder.

Methods: Thirty-four male subjects on probation/parole who met DSM-IV criteria for ASPD, and 30 male healthy comparison subjects, matched by ethnicity, were recruited from the community. The Barratt Impulsiveness Scale (BIS-11) provided an integrated measure of trait impulsivity. Rapid-response impulsivity was assessed using the Immediate Memory Task (IMT), a continuous performance test. Reward delay impulsivity was assessed using the Two-choice Impulsivity Paradigm (TCIP), where subjects had the choice of smaller-sooner or larger-delayed rewards, and the Single Key Impulsivity Paradigm (SKIP), a free-operant responding task.

Results: Compared to controls, subjects with ASPD had higher BIS-11 scores (Effect Size (E.S.)=0.95). They had slower reaction times to IMT commission errors (E.S.=0.45). Correct detections, a measure of attention, were identical to controls. On the SKIP, they had a shorter maximum delay for reward (E.S.=0.76), but this was not significant after correction for age and education. The groups did not differ on impulsive choices on the TCIP (E.S.<0.1). On probit analysis with age and education as additional independent variables, BIS-11 score, IMT reaction time to a commission error, and IMT positive response bias contributed significantly to diagnosis of ASPD; SKIP delay for reward did not. Severity of ASPD, assessed by the number of ASPD symptoms endorsed on the SCID-II, correlated significantly with commission errors (impulsive responses) on the IMT, and with liberal IMT response bias. This relationship persisted with correction for age and education.

Discussion: These results suggest that ASPD is characterized by increased rapid-response impulsivity. Aspects of impulsivity related to reward-delay or attention appear relatively intact.

Figures

Figure 1
Figure 1
ASPD symptoms and IMT commission errors (r = 0.62, n = 25, p = 0.001). The horizontal axis shows the rate of IMT commission errors as a percentage of stimuli with 4 of 5 digits correct. The vertical axis shows the number of ASPD symptoms endorsed (SCID-II).

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