Brain mechanisms of disordered gambling

The DSM-5 Work Group also paid careful attention to recent research on the underlying pathophysiology of disordered gambling. Neuropsychological studies in pathological gamblers have identified core deficits in risky decision-making, which resemble the changes observed in patients with brain lesions with damage to the ventromedial prefrontal cortex. Pathological gamblers place higher wagers on simple probability decisions, ^{Reference Lawrence, Luty, Bogdan, Sahakian and Clark7} they are less likely to choose delayed rewards over immediate gratification, ^{Reference Petry8} and they struggle to learn the advantageous tactic on a test that pits short-term gains against long-term penalties. ^{Reference Goudriaan, Oosterlaan, de Beurs and van den Brink9} These indications remind us, at a clinical level, of their predisposition towards poor risk evaluation and persistent play in the face of mounting debt. In substance use disorders, these neurocognitive measures have value in predicting short-term treatment outcomes. ^{Reference Bowden-Jones, McPhillips, Rogers, Hutton and Joyce10} However, the neuropsychological data do not carry unequivocal implications for grouping these disorders, as these deficits could equally be used to support the classification of pathological gambling alongside attention-deficit hyperactivity disorder or bipolar affective disorder, for example.

The neuropsychological research is now complemented by neuroimaging studies that directly illuminate underlying brain substrates. Potenza and colleagues ^{Reference Potenza11} have used functional magnetic resonance imaging to monitor brain responses while pathological gamblers viewed gambling videos and performed tasks of self-control. Cocaine addicts in their lab have undergone comparable procedures in the scanner. Both groups showed impaired recruitment of the ventromedial prefrontal cortex region during both procedures, in contrast to healthy controls. ^{Reference Potenza11} A separate study had pathological gamblers complete a simple card game where they could win or lose €5 on each trial. The brain responses in dopamine-rich reward circuitry were attenuated, and some of these changes were proportional to gambling severity. ^{Reference Reuter, Raedler, Rose, Hand, Glascher and Buchel12} As the activation tasks in these studies become more sophisticated, it is proving possible to quantify some of the more subtle cognitive distortions seen in problem gamblers, such as the impact of near-miss outcomes ^{Reference Clark5} and loss-chasing decisions. ^{Reference Campbell-Meiklejohn, Woolrich, Passingham and Rogers13} However, it should also be noted that these neuroimaging studies are few in number, used small numbers of participants, and the findings may again cut across several disorders and suggest pathophysiology shared with multiple conditions.

These neurobiological conceptualisations run the risk of assuming that pathological gamblers represent a homogeneous group. This is unlikely to be true. The Pathways Model explicated by Blaszczynski & Nower ^{Reference Blaszczynski and Nower14} (although not as yet fully validated) hypothesises three routes into disordered gambling. Individuals in the first group have no predisposing vulnerabilities; rather their gambling problems have been conditioned by the psychological properties of the games themselves, and perhaps by the experience of a ‘big win’ early in their gambling careers. The second subgroup is prone to depression or anxiety, and these individuals begin gambling as a means of escape or to otherwise alleviate these emotional difficulties. The third group present with antisocial and impulsive tendencies, accompanied by neuropsychological evidence of frontal cortex involvement, and it may be this subgroup that is characterised in the neurobiological studies in clinical groups described above.

Decisions in the diagnosis of pathological gambling

Two further changes in the diagnosis of pathological gambling are likely in the DSM-5. The decision to rename the illness ‘disordered gambling’ has been prompted by confusion between the terms pathological gambling and ‘problem gambling’. Epidemiological data ^{Reference Toce-Gerstein, Gerstein and Volberg15} demonstrate that substantial harms from gambling exist in many individuals who do not meet the formal DSM-IV cut-off of five symptoms from the ten listed, leading some to use the term ‘problem gambler’ somewhat indiscriminately. The British Gambling Prevalence Survey ^{Reference Wardle, Sproston, Erens, Orford, Griffiths and Constantine16} adopted a more liberal threshold of three DSM symptoms for detection of ‘problem gambling’ (see below). Having proposed to abolish the general distinction between drug ‘abuse’ and ‘dependence’, the DSM-5 Work Group are continuing to source evidence on the precise placement of the threshold for diagnosing disordered gambling.

A further modification is the removal of one of the ten criteria, which asks whether the gambler has committed any illegal acts to support their gambling. Besides the obvious point that people may be unwilling to disclose this information, two epidemiological studies have shown that this item is only reliably endorsed by the most severe pathological gamblers who already meet most of the other listed criteria, and as such, the ‘illegal acts’ item adds little discriminatory power. ^{Reference Toce-Gerstein, Gerstein and Volberg15,Reference Strong and Kahler17} However, this conclusion has been derived from work in adult populations, and it is conceivable that the illegal acts item may have more utility in specific populations such as adolescents. ^{Reference Mitzner, Whelan and Meyers2} Our clinical experiences suggest that it can be highly informative to assess whether the moral line into criminal activity has been crossed in the pursuit of gambling funds.

The National Problem Gambling Clinic

International guidelines such as the DSM must be considered at a national level, in the specific context of gambling within British society. The 2007 British Gambling Prevalence Survey ^{Reference Wardle, Sproston, Erens, Orford, Griffiths and Constantine16} found that 68% of those interviewed reported gambling in the past year, which is similar to a lifetime rate of 78% reported in a US survey. ^{Reference Kessler, Hwang, LaBrie, Petukhova, Sampson and Winters18} Evidently, gambling is a major branch of the entertainment industry and appeals to the majority of the population. The most common forms of gambling in the UK are the National Lottery, scratch cards, horse racing, and slot machines. For disordered gambling, the lifetime prevalence of DSM pathological gambling was 1–2% in a North American meta-analysis, ^{Reference Shaffer, Hall and Vander Bilt19} and the past-year prevalence of problem gambling was 0.6% in the 2007 British survey. The report from the 2010 British Gambling Prevalence Survey shows the past-year prevalence of gambling to have risen to 73% of the adult population. The prevalence of problem gambling has also increased to an estimated 0.9% of the population. Future analysis of data will look closely at internet gambling and its harms. ^{Reference Wardle, Moody, Spence, Orford, Volberg and Jotangia20}

The National Problem Gambling Clinic was opened in October 2008 as the first National Health Service facility specifically set up to treat problem gamblers. At the time of writing, we have received over 700 referrals, from across the UK. The treatment approach is evidence-based, with a cognitive-behavioural therapy (CBT) formulation ^{Reference Gooding and Tarrier21} complemented with family therapy and debt counselling. Acknowledging the multiple pathways into problem gambling, we offer several levels of intervention, from weekly CBT group sessions lasting 9–12 weeks through to individual treatment designed for dual diagnosis clients. Our multidisciplinary team consists of psychologists, psychiatrists, family therapists and financial advisors, all working according to standardised protocols. The clinic maintains a strong research focus, the data recording is extensive and initial findings are in preparation. For further information, or to make a referral, please see our website www.cnwl.nhs.uk/gambling.html or email us at [email protected].

Future directions

We believe the DSM-5 proposals for reclassification will be popular with problem gamblers and gambling support groups, who have long considered gambling to be an addictive behaviour with a similar potency to drugs or alcohol. The nosological changes are likely to enhance research funding in the area, as gambling researchers may benefit from funding mechanisms ring-fenced for addiction research (e.g. the Medical Research Council’s current Addiction Research Strategy). But of course, profound theoretical issues are also raised about the true nature of addiction, and some experts in drug addiction oppose the changes. ^{Reference Holden1} Other candidate behavioural addictions exist in the form of compulsive shopping, excessive online videogame play and internet addiction, ^{Reference Block22} but in preparing the DSM-5, the research literatures on these conditions were considered premature for evidence-based reclassification. If we accept that gambling is addictive, then what psychological properties of gambling games enable them to harness the motivational systems of the brain so effectively? By answering this question, we will be better placed to judge in future which other conditions should be added to the behavioural addictions.

Funding

H.B.-J. and L.C. have received funding from the Medical Research Council (grant ). L.C. also receives grant funding from the Royal Society for research into the brain mechanisms of problem gambling. The National Problem Gambling Clinic is funded by the government’s Responsible Gambling Fund.