Pathological Gambling and Dopamine Synthesis in the Dorsal and Ventral Striatum
Author: Mark Gold, MD
Pathological gambling is a significant problem in the United States, impacting millions of adults, teens and their families. According to the National Council on Problem Gambling, approximately one to two percent of adults in the United States are compulsive gamblers, and this number appears to be increasing. Another two to three percent have somewhat less significant, but nevertheless significant, problems with gambling that often results in harmful consequences for themselves and for their loved ones. These persons are classified as problem gamblers.
According to the American Psychiatric Association, characteristics of gambling addiction include:
- Preoccupation with gambling (for example, relives past gambling experiences, handicaps or plans the next venture, thinks of ways to get money with which to gamble)
- Tolerance, the need to gamble with increasing amounts of money to achieve desired level of euphoria
- Making repeated and unsuccessful attempts to stop or curtail gambling
- Becoming bored, restless or irritable when they cannot gamble
- Lying to family members to conceal the extent of involvement with gambling
- Committing illegal acts such as theft, forgery, fraud, etc, to finance their gambling
- Loss of or jeopardizing an important relationship, job or educational opportunity because of gambling
The prevailing theory on pathological gambling is that it is a “process addiction” wherein the gambler’s brain’s reward center has been hijacked in much the same way it is when one is addicted to intoxicants – that is, mediated by the central dopamine system.
Yet to date, there is little direct evidence showing a significant difference in brain anatomy or function between pathological gamblers and healthy controls. A recent study by van Holst, et al., (2017) provides such evidence. Van Holst and colleagues utilized dynamic positron emission tomography (PET) scans and compared dopamine synthesis capacity in the dorsal and ventral striatums of 13 pathological gamblers and 15 healthy controls.
The results were both clear and confounding. Dopamine synthesis capacity was significantly higher in pathological gamblers when compared with healthy control subjects. Specifically, dopamine synthesis was 16% higher in the caudate body, 17% higher in the dorsal putamen and 17% higher in the ventral striatum among pathological gamblers. Yet functional magnetic resonance imaging (fMRI) studies have shown both higher and lower striatal activity during both anticipation and upon outcome notification of monetary rewards, which is the “brass ring” in gambling addiction.
These seemingly contradictive findings appear to make it impossible to show that gambling is associated with static deficits in dopamine volume or function as are the case with other addictions. To clear up these contradictions, Luijten, et al., conducted a meta-analyses of fMRI data to summarize results from many studies of reward processing in addiction.
Clearly, there are both methodological issues to be addressed as well as an imperative to understand why the diverse findings exist in addicted gamblers. Studies need to be designed to describe the mechanisms that result in the differing outcomes observed in the striatum of addicted gamblers.
Why Does This Matter?
Process or behavioral addictions have been increasing worldwide. But what is an addiction versus what is a choice is the hard question that is more difficult to discern in process addictions. Sex, food, games and other behaviors have been debated, but only gambling has made it to the official addiction list of the DSM 5.
But gambling opportunities are increasing and becoming more normalized, which begs the question: are state lottery games the gateway drug to gambling addiction? Drive by a convenience store the day before the big jackpot, and observe the people spending perhaps half their paycheck on a 1-in-80 million chance to win. As the gambling industry pervades the mainstream of society, there will be more pathological gamblers.
But now there is good, high quality evidence that pathological gambling is like other addictions in that it too involves dopamine availability and function in the brain’s reward region, specifically increased striatal dopamine synthesis among pathological gamblers. These findings open the door for future research and hopefully new treatments for suffering gamblers, who are at high risk for homelessness, other mental illness and suicide.