Abstract

Impulsive-compulsive behaviours (ICBs) are an increasingly well-recognised side-effect of dopaminergic medications used to treat Parkinson's disease (PD). These include pathological gambling, hypersexuality, compulsive shopping, binge eating, punding and compulsive use of DRT, or dopamine dysregulation syndrome. The association between these ICBs and other behaviours such as impulsive smoking, excessive hoarding, impaired sleeping and reckless generosity has recently been described.

Mechanisms implicated in the development and perpetuation of ICBs in PD includes altered learning from reward-related situations, increased risk preferences, and a strong preference for immediate over future rewards. These cognitive processes are modulated by dopamine, and the use of dopamine replacement therapy is strongly associated with ICBs in PD. However, the amounts used do not predict the development of these behaviours, which suggests an underlying vulnerability among some PD patients to the behavioural side-effects of these medications. A “global sensitisation” of ventral striatal reward circuitry has been proposed as an important pathogenic mechanism for ICBs in PD, which may explain the frequent co-occurrence of different ICBs in an individual. This is suggested by recent functional imaging of ICBs, which strengthens the link between the drug addiction literature.

Treatment options for ICBs in PD remain somewhat limited, including pharmacological, surgical and psychological interventions. Increased awareness of these behaviours among clinicians, patients and carers is crucially important to prevent their development in vulnerable patients.