Elsevier

Biological Psychiatry

Volume 51, Issue 12, 15 June 2002, Pages 988-994
Biological Psychiatry

Original article
Two models of impulsivity: relationship to personality traits and psychopathology

https://doi.org/10.1016/S0006-3223(01)01357-9Get rights and content

Abstract

Background: Impulsivity is prominent in psychiatric disorders. Two dominant models of impulsivity are the reward-discounting model, where impulsivity is defined as inability to wait for a larger reward, and the rapid-response model, where impulsivity is defined as responding without adequate assessment of context. We have compared the role of these models of impulsivity in human psychopathology, based on the hypothesis that rapid-response impulsivity would be more strongly related to other aspects of psychopathology and to impulsivity as described by questionnaires.

Methods: We investigated relationships between personality and laboratory measures of impulsivity, and between these measures and clinical characteristics, in parents of adolescent subjects with disruptive behavioral disorders (DBDs) and matched control subjects. Diagnoses were rendered using the Structured Interview for DSM-IV. The Barratt Impulsiveness Scale (BIS) was used as a trait measure of impulsivity. Rapid-response impulsivity was assessed using a form of the Continuous Performance Test, the Immediate Memory-Delayed Memory Task (IMT/DMT). Reward-delay impulsivity was measured using two tasks where subjects could choose between smaller immediate or larger delayed rewards.

Results: Rapid-response, but not reward-delay impulsivity, was significantly higher in subjects with lifetime Axis I or Axis II diagnoses. Scores on the BIS were elevated in subjects with Axis I diagnoses and correlated significantly with both rapid-response and reward-delay tests, but more strongly with the former. Multiple regression showed that rapid-response, but not reward-delay performance or intelligence quotient, contributed significantly to BIS scores. Correlations were similar in parents of control subjects and of DBD subjects.

Conclusions: These data suggest that measures of rapid-response impulsivity and of reward-delay impulsivity are both related to impulsivity as a personality characteristic. The relationship appears stronger, however, for rapid-response impulsivity, as measured by the IMT/DMT. Laboratory and personality measures of impulsivity appear to be related to risk of psychopathology.

Introduction

Impulsivity is a component of the initiation of behavior Barratt and Patton 1983, Evenden 1999a. It appears to be a basic part of disruptive behavior disorders (Dougherty et al 2000), substance abuse (Allen et al 1998), personality disorders (Mulder et al 1999), aggression (Barratt et al 1999), bipolar disorder (Swann et al 2001), suicide (Corruble et al 1999), and other potentially destructive behavioral problems (Brady et al 1998). Rigorous definitions have been elusive: impulsivity can be a component of any motivated behavior, and it can have multiple expressions, including neurophysiology, laboratory performance, and action (Barratt and Patton 1983).

Research on impulsivity has generally relied on self-report, or on measurements or observations of behavior whose impulsivity was open to interpretation Barratt and Patton 1983, Johnson et al 1998. These measures have yielded valuable information about impulsivity as a stable trait in individuals with a wide range of behavioral disturbances (Barratt and Patton 1983). They do not, however, lend themselves well to pharmacologic or physiologic studies of impulsivity, because they are subjective, they measure a relatively stable characteristic, and they cannot be related directly to biological models of impulsivity based on animal studies.

Laboratory measures of impulsivity have been developed in an effort to overcome these problems. These measures are based on two animal models of impulsivity: inability to delay reward, leading to an increased tendency to choose immediate small rewards over larger delayed ones (Monterosso and Aimslie 1999); and inability to conform responses to environmental context, leading to errors of commission on tests that required careful checking of stimuli (Evenden 1999b). There is little information, however, relating measures of these models of impulsivity to each other or to established personality measures.

We have compared the two dominant models of laboratory impulsivity in parents of subjects and control subjects who participated in an investigation of disruptive behavior disorders. Impulsivity as a stable personality trait was measured using the Barratt Impulsiveness Scale (BIS) total and subscale scores (Patton et al 1995). Rapid-response impulsivity was measured using the Immediate Memory-Delayed Memory Task (IMT/DMT), a version of the Continuous Performance Test that has been used successfully in studies of individuals at risk for severely impulsive behavior (Dougherty 1999). Reward-delay impulsivity was measured by the Two-Choice Test (Cherek and Lane 1999) and the Single Key Impulsivity Paradigm (Dougherty et al, manuscript in review), both of which measure the tendency to choose small immediate rewards over larger delayed ones. Our hypothesis was that rapid-response impulsivity would be more strongly related to human psychopathology, as reflected by 1) stronger relationship to presence of a psychiatric diagnosis; 2) stronger relationship to BIS scores; and 3) stronger relationship to overall personality disturbance as reflected by Structured Clinical Interview for DSM-IV Axis II Personality Disorders (SCID-II) responses.

Section snippets

Subjects

Each subject was a biological parent of a participant (patient or matched control subject) in a study of adolescent inpatients with disruptive behavior disorders (DBDs) including oppositional defiant disorder, conduct disorder, and attention-deficit/hyperactivity disorder (ADHD). Twenty-two (19 women and 3 men, mean age 43 years, range 34–55 years) were parents of control subjects, and 10 (8 women and 2 men, mean age 39.7, range 32–47) were parents of subjects with DBDs. The groups did not

Rapid-response

Table 1 shows that total and nonplanning BIS scores correlated significantly with commission error rates on both the IMT and DMT. The pattern of correlations was strongest for BIS nonplanning scores. Although correlations did not reach significance in parents of subjects with DBDs, owing to the small number, the regression was essentially identical for the two groups, as shown in Figure 1.

Reward-delay

SKIP. In the SKIP, the total number of free-operant reward-directed responses correlated significantly

Discussion

Commission errors on the IMT/DMT, a potential measure of rapid-response impulsivity, (Halperin et al 1991), correlated with Barratt Impulsiveness Scale scores. Reward-delay measures did not correlate as strongly with BIS scores and did not contribute significantly to a multiple regression model. IMT/DMT performance was also more strongly related to the presence of an Axis I or Axis II diagnosis and to overall personality disturbance as reflected by SCID-II results. These data suggest that the

Acknowledgements

Supported by the Pat R. Rutherford, Jr. Chair in Psychiatry (ACS) and AA 12046 (DMD).

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