Opioids are a group of powerful drugs and medications directly or indirectly made from a plant called the opium poppy. All opioids reach the brain through sites, called opioid receptors, found on the surfaces of certain types of cells. In a study presented in October 2014 to the European College of Neuropsychopharmacology, a team of researchers from the United Kingdom examined changes in the opioid receptors of people affected by gambling disorder, a form of non-substance-based behavioral addiction. The researchers concluded that people who are problem gamblers\u00a0undergo detectable changes in their normal opioid receptor function. Gambling Disorder Within the span of a single year, people diagnosed with gambling disorder have at least four symptoms of an unhealthy, damaging relationship to participation in at least one type of gambling activity. At the extreme, an affected person can have nine such symptoms. The disorder can affect a person who only gambles at physical locations like casinos, only gambles virtually over the Internet or gambles at physical locations and over the Internet. While some affected individuals only experience problems with one specific gambling game or activity, others have problems with two or more games or activities. In the U.S., gambling disorder is the only form of non-substance-related behavioral addiction officially recognized and defined by the American Psychiatric Association (APA), an organization that has set the country\u2019s most widely accepted criteria for all diagnosable mental health problems for more than half a century. A person with a behavioral addiction exhibits some of the key behavioral changes and brain function alterations found in individuals with substance addictions. However, their problems stem from repeated, dysfunctional involvement in commonplace, substance-free activities that cause no harm to the vast majority of participants. The APA uses the term addictive disorder to classify gambling disorder instead of the more broadly used term behavioral addiction, or another lesser-used term, process addiction. Opioid Receptors All humans have four types of opioid receptors, most of which are located in the brain, spinal cord or intestinal tract. These receptors are used by naturally occurring chemicals in the body (including the well-known endorphins) that help relieve pain. The brain also uses the opioid receptors to help generate pleasure as a reward for participating in such life-sustaining activities as eating nutrient-rich food and having sex. As their name implies, opioid receptors also provide brain access for opioid drugs and medications; in addition, alcohol and stimulant drugs like cocaine produce some of their effects by accessing the brain through the opioid receptors. Essentially all recreational or medicinal substances that trigger these receptors have the ability to produce physical dependence and addiction. Gambling Disorder and the Opioid Receptors In the study presented to the European College of Neuropsychopharmacology, researchers from universities in Cambridge and London used a small-scale project to examine the changes in opioid receptor function found in people with gambling disorder. A total of 29 people took part in this project. Fourteen of the participants had diagnosable symptoms of gambling disorder. The remaining 15 participants did not have gambling problems. The researchers used imaging procedures called PET scans to count the number of opioid receptors in the brains of both groups of participants. After completing this examination, they concluded that people with gambling disorder have just as many opioid receptors as people unaffected by the condition. Next, the researchers gave the members of both groups a dose of amphetamine that triggered the release of their bodies\u2019 naturally occurring endorphins. Each study participant then went through a second PET scan. The researchers concluded that, compared to people unaffected by gambling disorder, people affected by this behavioral addiction release fewer endorphins in response to amphetamine exposure. In turn, this reduced level of endorphin response leads to a smaller pleasurable reaction to the amphetamine. The study\u2019s authors believe that the reduced level of endorphin release in the brains of people with gambling disorder may help explain why these people develop dysfunctional patterns of gambling involvement. This finding also helps confirm the reality of behavioral addiction in general as a condition capable of altering normal brain function, just like substance addiction. It\u2019s important to note that the changes produced by gambling disorder appear to have a clearly different impact on opioid receptor function than the changes produced by alcoholism or other forms of substance addiction.