Impulse control disorders in Parkinson disease: is cognitive-behavioral therapy worth a wager?

Parkinson disease (PD) is now conceptualized as a neuropsychiatric disorder with characteristic motor features. It is increasingly recognized that standard dopaminergic treatments, particularly dopamine agonist drugs, can trigger devastating impulse control behaviors (ICB) in patients with PD. ICB encompass impulse control disorders (ICD) and related disorders such as dopamine dysregulation syndrome (DDS), punding (stereotyped behaviors), and hobbyism. These disorders are linked by being rewardor incentive-based, and involve repetitive and compulsive acts despite potential long-term harmful consequences. ICB affected 13.6% of patients with PD in the largest North American multicenter study, including compulsive shopping (5.7%), pathologic gambling (5%), hypersexuality (3.5%), and compulsive eating (4.3%). This may be an underestimate since patients commonly fail or decline to declare them. Such behaviors exist on a continuum, and an increased interest in sex or hobbies may be viewed initially as a beneficial effect of treatment. However, ICB eventually may result in catastrophic financial, psychological, legal, and social consequences. In this issue ofNeurology®, Okai et al. report a novel randomized controlled trial comparing the effect of 12 weekly sessions of a cognitive-behavioral therapy (CBT) intervention to standard medical care (SMC) on ICB in PD with a 6-month follow-up. The primary outcomes of global symptom severity and neuropsychiatric disturbance improved in the CBT group. Disappointingly, caregiver stress and burden was not affected in the intervention group, although general psychiatric morbidity in caregivers was improved. These findings are potentially important as there is a dearth of robust evidence to guide management. ICB may have a strong biological basis with an imbalance between aberrant or excessive dopaminergic stimulation and inhibition of higher cortical control. This is reflected in current management. The “first choice” intervention is often the reduction or withdrawal of dopamine agonist therapy. This strategy may result in unsatisfactory outcomes, including loss of motor control, intolerance, or maladherence by the patient; and occasionally, the dopamine agonist withdrawal syndrome may occur, with the development of dysphoric symptoms likened to drug craving. Limited evidence exists for therapies such as selective serotonin reuptake inhibitor antidepressants, acetylcholinesterase inhibitors, anticonvulsants, and deep brain stimulation surgery. A role for CBT is sometimes, erroneously, regarded as a challenge to a biological view of etiology. As with any enriched environmental experience, CBT has the potential to bring about structural and functional brain changes. Clinicians should avoid the trap of viewing this in a Cartesian dichotomy. The case for more consideration of psychological and social factors in understanding ICB is compelling. Risk factors for PD ICB include a family history of gambling or addiction disorders which may point to not only genetic but also social factors. Being unmarried, greater depressive states or traits, anxiety, or obsessive-compulsive symptoms are also strongly associated with a propensity to ICB. Psychological interventions, including CBT, have been useful in managing ICB in non-PD populations. The current study is original regarding intervention, but has limitations. Bias may have occurred as the study was largely unblinded and the randomization procedure was relatively weak. Although adequately powered, it was a small convenience sample. The authors developed their own Impulse Control Behavior Severity Scale for the study, and the summative approach used in scoring may be open to question. No formal measures of executive function were recorded. No data were collected on the prevalent ICB source population, and the study group was largely younger men with PD. While this is a “typical” PD ICB profile, generalizability to other demographic ICB groups is less certain. Managing patients who have limited insight or behave covertly is challenging in practice. These patients may not have been adequately represented in this study. Physicians were asked to keep medication constant although changes were not precluded. At study commencement, more patients were receiving dopamine agonist drugs in the SMC group (65% vs 46%) than the treatment group. This may be clinically relevant. Interestingly, at 6 months follow-up, 44% of the treatment