Personality Components of Addiction
Unplanned, spontaneous reaction to a stimulus without regard for adverse consequences is the hallmark of impulsivity. Insensitivity to consequences is a critical prerequisite for addiction. Impulsivity impels the choice of immediate rewards over the promise of delayed, albeit greater, rewards. Early in addiction, impulsivity is a strong impetus for experimenting with drugs.
Disinhibition is a close relation to impulsivity; it is a tendency to engage in risk-taking, sensation-seeking behaviors without constraints. Like impulsivity, disinhibition involves a loosening of self-regulatory controls and a disregard for the potentially disastrous consequences of maladaptive behavior. Both traits closely dovetail with the salient elements of addiction: behavior that confers a pleasure, benefit, or relief from an internal stress; behavior that has escaped the person’s control; and behavior that is continued despite negative consequences.
Addiction cannot be understood without the concept of executive function. An umbrella term rather than an individual trait, executive function is a kind of supervisory cognitive process that integrates complex processes and mechanisms that govern behavior. The purview of executive function, which is anchored within the prefrontal cerebral cortex, includes reasoning skills, purposeful decision making, and the capacity to fend off distraction. Conscious control of thoughts and actions is implicit in executive function. When the interaction of emotional processing with behavioral restraints becomes impaired, addictive behavior and compulsions can take hold. Deficits in these mechanisms predispose and contribute to addiction.
Impulse-Control Disorders and Addiction
In accord with current research findings, the term addiction is likely to encompass behaviors and substances. Impulse-control disorders (ICDs) are a group of related behavioral disorders listed in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). The traditional ICDs include compulsive gambling, kleptomania, and pyromania.
The person with an ICD cannot resist the impulse to engage in potentially harmful behavior despite negative consequences—even possible criminal charges. Some internal tension precedes the behavior, which the behavior alleviates. A person with an ICD is typically a high scorer on measures of impulsivity and sensation-seeking. Descriptions of disinhibition, impulsivity, substance addiction, and behavioral addiction have obvious parallels; loosened controls and lessened restraints are integral to all. Distinctions between ICDs and substance addictions have blurred, in particular because similarly impaired neurophysiologic mechanisms underlie both.
Compulsive gambling has been termed a behavioral, or nondrug, addiction. It has been extensively studied as a model of the addiction process, in part because it does not cause the confounding effects of drugs on the brain. Defective processing of rewards and punishment, implicated in substance addiction, is a characteristic of compulsive gamblers. Sensitivity to monetary gains and losses alike is decreased. Compulsive gamblers will choose immediate monetary gains over the promise of higher, but delayed, gains. Known as delay discounting, this pattern reflects maladaptive decision making and impaired executive functioning. The trait predicts relapse in compulsive gambling.
Changes in the Brain
Whether it involves a substance or a behavior, addiction has a neurobiologic basis. The compulsions and lack of control that characterize addiction have counterparts in the brain’s neurophysiology. Neuroimaging techniques have made it possible to trace addiction-related personality traits to metabolic activity in specific parts of the brain.
Regions of the prefrontal cerebral cortex exercise control over most facets of personality that participate in addiction: notably, decision making and regulation of emotion-laden behavior. In addition to inhibitory control functions, frontal cortical regions govern the reward-related behavior that is impaired in addicted persons. Chronic substance abusers have shown, in studies that measure neuropsychologic traits, deficits in decision making and in executive and inhibitory abilities. These impairments parallel abnormalities in areas of the prefrontal cortex observed in neuroimaging studies.
Abnormal metabolic activity in persons with substance dependence has been observed in the orbitofrontal cortex, a specific area in the prefrontal cortex (directly behind the forehead). This region is thought to be a major participant in critical executive functions—emotional processing, impulse control, working memory. Dysfunction in the orbitofrontal cortex impairs the ability to assess future consequences. It is the orbitofrontal cortex that will direct a decision to set aside immediate gratification in favor of greater delayed rewards.
Involvement of the neurotransmitter dopamine is further evidence of neural participation in addictive processes. Dopamine is believed to act on mechanisms of expectation and reward. Cocaine and amphetamines both increase dopamine levels and dopaminergic transmission. Appetizing food and addictive drugs have a comparable effect in raising levels of extracellular dopamine.
Personality traits that pervade neurophysiologic and neuropsychologic studies of addiction also emerge in genetic studies. Genes apparently make an early contribution to addictive behaviors, determining expression of the vulnerabilities that promote addiction. The finding of high heritability for behavioral disinhibition is based on samples of adolescent monozygotic and dizygotic twin pairs. Genetically determined predisposition to behavioral disinhibition, which is related to early-onset substance addiction, is expressed in parts of the brain affecting impulsivity and reward systems. Genetic studies have linked several genes to impulsivity and addiction. Alcohol, nicotine, and cocaine addictions have particularly strong genetic roots.
Bibliography
Erickson, Carlton K. The Science of Addiction: From Neurobiology to Treatment. New York: Norton, 2007.
Holloran, Patricia. Impaired: A Nurse’s Story of Addiction and Recovery. New York: Kaplan, 2009.
Van Wormer, Katherine, and Diane Rae Davis. Addiction Treatment: A Strengths Perspective. 2nd ed. Stamford, CT: Cengage, 2007.
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