Abbreviations: PET, positron emission tomography; COMT, cathechol-o-methyl transferase; MAO, monoamine oxidase; CBT, cognitive behaviour therapy; PD, parkinson's disease; GD, gambling disorder
IntroductionImpulse control disorders such as compulsive gambling or compulsive shopping or uncontrollable sexual and eating behaviour, are well-recognized complications of Parkinson's disease (PD). They occur in up to 20% of PD patients.1 These disorders impair quality of life and function, place incalculable burdens on interpersonal relationships and on caregivers, and are associated with significant psychiatric co-morbidity.2 The Diagnostic and Statistical Manual of Mental Disorders, 5 th edition (DSM-V) 3 has classified Gambling Disorder (GD), previously viewed as an impulse control disorder, as a behavioural addiction. To qualify for this diagnosis, patients must meet at least four of the following nine criteria in the course of one year: a. Gambling increasing amounts of money in order to keep obtaining the same level of excitement.b. Experiencing restlessness or irritability when trying to stop gambling.c. Trying repeatedly and unsuccessfully to stop.d. Being constantly preoccupied with gambling.e. Gambling when distressed.f. Continually returning to gambling in order to make up for monetary losses.g. Covering up the extent of one's involvement in gambling.h. Jeopardizing relationships and careers because of gambling.i. Borrowing money from others to cover gambling debts.Gambling can be viewed as an impulse disorder or as an addiction. There are many forms of gambling, including card games, electronic games, betting on results of athletic or political contests. The most frequent forms of gambling in North America are reportedly playing the slot machines, buying lottery scratch cards and playing bingo. Having a gambling addiction means preferentially selecting immediate, albeit risky, opportunities to make money instead of relying on a longer-range strategy that is both safer and more lucrative. A small amount of immediate gain takes precedence for the pathological gambler over a larger gain that requires a period of waiting. Decisions made by pathological gamblers appear to be rash, with little thought of probable consequences such as financial burden, interference with career, or dissolution of family bonds. Immediate satisfaction is valued over potential risks. Even repeated negative consequences do not seem to act as deterrents. Individuals with PD who suffer from GD exhibit uncontrollable cravings, develop tolerance, and experience withdrawal symptoms in the same way as those who suffer from drug or alcohol addiction, and there is a high degree of co-morbidity between these conditions.
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AimThe aim of this brief overview is to determine whether GD can help to shed light on the etiology of Parkinson's disease, and whether aspects of Parkinson's disease, including its treatment, can help to clarify the basis of GD.
MethodThere is a substantial literature on GD in Parkinson's. Via the PubMed database, articles fr...