One of the many interesting shifts in DSM-5 was the reclassification of pathological gambling from the impulse control disorders category to substance addictions (“substance-related and addictive disorders”). The shift effectively recognized (the now re-labeled) “gambling disorder” as the first behavioral addiction. This is a fascinating construct in psychiatry. The other diagnoses in this category involve the compulsive administration of exogenous drugs. Much of our knowledge of addiction comes from studying the pharmacology of these drugs and their ability to “hijack” reward-oriented behavior in animal models.

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In the case of gambling disorder, there is no exogenous substance; rather, there is excessive engagement in a behavior in which money is wagered on the uncertain prospect of a larger monetary prize. Even the role of money is unclear in this equation. While money is self-evidently a potent incentive, at a psychological level, it is a complex, learned reinforcer (as distinct from a natural reward, such as food or sex). For at least some gamblers, winning money appears to play a negligible role in maintaining their behavior.¹

So what is it about this behavior that enables gambling to yield a power that is comparable to drugs such as cocaine, heroin, and alcohol? And might other behaviors, such as video gaming, food addictions, shopping, and sex, be conceptualized as addictive behaviors in the future?

Recognizing the disordered gambler

The DSM-5 diagnosis of gambling disorder uses a threshold of 4 of 9 symptoms. These symptoms have changed little from the original list in DSM-III, which was based on the diagnostic criteria for substance dependence. The symptoms include classic hallmarks of an addiction syndrome: preoccupation with gambling, gambling with larger amounts over time (akin to tolerance), and agitation when stopping gambling (akin to withdrawal).

The criteria also emphasize the negative consequences of gambling, such as occupational or interpersonal difficulties, borrowing money, and lying about gambling. Certainly, financial debt is ubiquitous in individuals with gambling disorder, and in the rare cases that do not involve significant debts, there is usually either some form of bailout from others or bankruptcy.

Gambling disorder is linked to high rates of criminal acts to support gambling, although clinicians should note that criminality was dropped as a specific criterion in DSM-5. Homelessness, physical health burden, and suicidal behavior are further corollaries that highlight the ultimately catastrophic downward spiral of gambling disorder.

Another feature that does not have an obvious counterpart in drug addiction is loss-chasing: continuing to play or returning to the venue at a later date in an effort to claw back recent debts. Loss-chasing is often regarded as a tipping point at which recreational gambling becomes problematic. In epidemiological datasets, loss-chasing is generally the most endorsed feature.² These population studies also illustrate how the harms of gambling are continuously distributed: individuals who do not meet diagnostic criteria can nonetheless experience clear harm from gambling. The prevalence estimates for “at risk” gambling are in the range of 2% to 7%, with full DSM diagnosis in 0.5% to 1%.³

Neurobiological correlates

One of the pivotal lines of evidence that shaped the DSM-5 reclassification was the neurobiological overlap between gambling disorder and the substance use disorders. From a neurocognitive perspective, elevated impulsivity is a reliable feature in patients with gambling disorder.⁴ This personality trait refers to the tendency for rapid responses and unplanned decisions. It can be measured with either questionnaires or behavioral tasks, and is conceptualized as arising from an imbalance between overactive subcortical reward systems and underactive prefrontal cortical control mechanisms.⁵ Similar cognitive markers are apparent in substance use disorders.⁴ Impulsivity tends to predate gambling disorder as well as other addictions, with predictive value from early childhood.⁶

Neuroimaging experiments have begun to characterize the underlying neural basis of gambling disorder. Functional MRI studies illustrate changes in brain reward circuitry, centered on the ventral striatum and medial prefrontal cortex.⁷ This system is robustly activated in healthy volunteers by winning money and during risky gambling decisions.⁸ While these areas are abnormally recruited in persons with gambling disorder (and also in drug addicts), the precise nature of this pathophysiology is proving elusive, with reports of hypoactivity and hyperactivity in equal measure.⁷