CME credit for this article has now expired. The article appears her for informational purposes only.

Educational Objectives

After reading this article, you will be familiar with:

• Differences and similarities between impulsivity and compulsivity.
• Characteristics of impulsivity and compulsivity.
• Factors that contribute to impulsivity and those that contribute to compulsivity.
• Treatment approaches for impulsivity and compulsivity..

Who will benefit from reading this article?
Psychiatrists, primary care physicians, neurologists, nurse practitioners, and other health care professionals. Continuing medical education credit is available for most specialists. To determine whether this article meets the continuing education requirements of your specialty, please contact your state licensing board.

Dr Berlin is assistant professor and Dr Hollander is Esther and Joseph Klingenstein Professor and chair, department of psychiatry at Mount Sinai School of Medicine in New York; Dr Hollander is also director of the Seaver and New York Autism Center of Excellence at Mount Sinai.

Dr Berlin reports no conflicts of interest concerning the subject matter of this article; Dr Hollander reports that he has received research grants from Solvay, Abbott, Ortho-McNeil, and Somaxon.

Impulsivity and compulsivity are natural behaviors controlled by brain mechanisms that are essential for survival in all species. Understanding these brain mechanisms may lead to targeted treatment strategies for these symptom domains when impulsivity and compulsivity become dysfunctional. Pathological impulsivity and compulsivity characterize a broad range of mental disorders and are the core and most debilitating symptoms, at least phenotypically, in some of the disorders in which these behaviors occur. These illnesses, some of which are highly heritable, are currently classified across several DSM-IV-TR diagnostic categories. Obsessive-compulsive spectrum disorders include obsessive-compulsive disorder (OCD), body dysmorphic disorder, trichotillomania, Tourette syndrome, and hypochondriasis. Disorders that involve deficits in impulse control include pathological gambling, externalizing disorders such as attention-deficit/hyperactivity disorder (ADHD), personality disorders such as borderline personality disorder, and substance and behavioral addictions.

Impulsivity versus compulsivity

The concept of impulsivity has many different aspects and definitions, but in general it covers a wide range of “actions that are poorly conceived, prematurely expressed, unduly risky, or inappropriate to the situation and that often result in undesirable outcomes,” or more simply put, a tendency to act prematurely and without foresight.¹ Moeller and colleagues² defined impulsivity as “a predisposition toward rapid, unplanned reactions to internal or external stimuli without regard to the negative consequences of these reactions to the impulsive individual or to others.” However, impulsivity is not always unplanned; for example, some pathological gamblers plan in advance to pursue their impulsive behavior. Impulsive behaviors can be conceptualized as the core symptoms of a broad range of psychiatric disorders that are often comorbid with one another, including cluster B personality disorders, impulse control disorders, and bipolar disorder (Figure 1 restricted. Please see print version for content.).

In contrast, compulsivity refers to repetitive behaviors that are performed according to certain rules or in a stereotypical fashion.³ Compulsivity is a tendency to repeat the same, often purposeless acts, which are sometimes associated with undesirable consequences. Impulsivity and compulsivity may be viewed as diametrically opposed, or alternatively, as similar, in that each implies a dysfunction of impulse control.⁴ Each involves alterations within a wide range of neural processes including, for example, attention, perception, and coordination of a motor or cognitive response. Objective neurocognitive tests hold potential for elucidating the mechanisms by which pharmacological agents exert their beneficial clinical effects and for predicting clinical outcomes.^5,6 Using sensitive and domain-specific neurocognitive tasks, we may also be able to divide impulsivity and compulsivity into separate and quantifiable neuro-biologically specific domains.⁷

Disorders characterized by impulsivity include impulse control disorders in DSM-IV-TR, representing a failure to resist aggressive impulses (as in intermittent explosive disorder) and urges to steal (kleptomania), set fires (pyromania), gamble (pathological gambling), and pull one’s hair (trichotillomania). However, behaviors characteristic of these disorders may also manifest as symptoms of another mental disorder. A number of other disorders are not included as a distinct category but are categorized as impulse control disorders not otherwise specified in DSM-IV-TR. These include sexual compulsions, compulsive shopping, skin picking, and Internet addiction. Impulse control disorders share the feature of the irresistible urge to act in a given way and may be considered as a subset of the obsessive-compulsive spectrum of disorders.

The obsessive-compulsive spectrum is a dimensional model of risk avoidance in which impulsivity and compulsivity represent polar opposite psychiatric spectrum complexes that can be viewed along a continuum of compulsive and impulsive disorders. Patients on the compulsive end of the spectrum tend to have an exaggerated sense of threat from the outside world and engage in rituals/routines, such as obsessive-compulsive behaviors, to neutralize the threat or reduce the harm. This end point marks compulsive or risk-aversive behaviors characterized by overestimation of the probability of future harm, as exemplified by OCD. However, some compulsive patients pursue unrewarding rituals for short-term gains (relief of tension) despite negative long-term consequences. Generally, however, OCD rituals are not pleasurable activities engaged in for their own sake but are neutral or often irritating and unpleasant behaviors that are performed to reduce anxiety.

Patients on the impulsive end of the spectrum tend to underestimate the harm that is associated with behaviors such as aggression, excessive gambling, or self-injury. This end point designates impulsive action generally characterized by a lack of consideration of the negative results of such behavior and is exemplified by borderline and antisocial personality disorders.⁸ Some impulsive patients do recognize and assess the harm associated with the impulsive behavior but nonetheless engage in it because they find that the thrill or arousal they experience in response to the behavior outweighs the negative consequences.

Impulsive behaviors generally have an element of pleasure, at least initially, although they may lose their pleasurable quality over time. Some patients with impulse control disorders may engage in the behavior to increase arousal, but there may be a compulsive component to their behavior in which they continue to engage in the behavior to decrease dysphoria. So, in general, while compulsivity may be driven by an attempt to alleviate anxiety or discomfort, impulsivity may be driven by the desire to obtain pleasure, arousal, or gratification. Both types of behaviors share the inability to inhibit or delay repetitive behaviors.⁹ Over time, impulsive behaviors may become compulsive (driven behaviors without arousal) and compulsive behaviors may become impulsive (reinforced habits).

Contributing factors

There are many contributing factors to impulsivity and compulsivity, such as genes, gender, environment, psychiatric disorders, and substance abuse. The neurobiology of impulsivity and compulsivity may involve inhibitory neurotransmitters such as serotonin and γ-aminobutyric acid (GABA); excitatory neurotransmitters such as glutamate, norepinephrine, and dopamine; and prefrontal cortex and/or limbic dysfunction. Convergent evidence suggests that a failure in top-down cortical control mechanisms that leads to striatal overdrive may constitute a unifying pathophysiological model underpinning an “impulsive-compulsive spectrum” of mental disorders.⁷ Increased frontal lobe activity may characterize the compulsive disorders, such as OCD. In contrast, decreased frontal lobe activity may characterize the impulsive disorders, such as pathological gambling and borderline personality disorder.⁹

Impulsive and compulsive features may present at the same time or at different times during the same illness.¹⁰ Although both compulsive and impulsive disorders may be related to prefrontal cortex dysfunction, compulsive disorders would be related to hyperactivity and impulsive disorders to hypoactivity of the prefrontal cortex. Compulsiveness appears to be associated with increased frontal lobe activity, while impulsiveness may be associated with reduced frontal lobe activity.