Impulse control disorders in Parkinson's disease: definition, epidemiology, risk factors, neurobiology and management

Abstract

There is increasing awareness that impulse control disorders (ICDs), including pathological gambling, hyper-sexuality, compulsive eating and buying, can occur as a complication of Parkinson's disease (PD). In addition, other impulsive or compulsive disorders have been reported to occur, including dopamine dysregulation syndrome (DDS) and punding. Case reports and prospective studies have reported an association between ICDs and the use of dopamine receptor agonists at higher doses, and DDS has been associated with l-dopa at higher doses or short-acting dopamine receptor agonists. Risk factors for ICDs include male sex, younger age or younger age at PD onset, a pre-PD history of ICD symptoms, history of substance use or bipolar disorder, and a personality profile characterized by impulsiveness. The management of clinically significant ICD symptoms should consist of modifications to dopamine replacement therapy, particularly dopamine receptor agonists, which is usually associated with an improvement of ICDs. There is no empirical evidence supporting the use of psychiatric drugs for ICDs in PD. Functional neuroimaging studies such as functional MRI and PET can investigate in vivo the neurobiological basis of these pathological behaviours.

Introduction

Impulse control disorders (ICDs) are characterized by the failure to resist an impulse, drive or temptation to perform an act that is harmful to the person or to others. It is very important to recognize ICDs because they can cause considerable distress to patients and caregivers, and can have disastrous personal, financial and socio-familial consequences. They are certainly underreported due to patients' embarrassment to admit to having them.

The formal ICDs are grouped together in a category entitled “ICDs not elsewhere classified” and include intermittent explosive disorder, kleptomania, pyromania, pathological gambling (PG), trichotillomania, and ICD not otherwise specified (ICD-NOS). Different psychiatric disorders characterized by impaired impulse control (e.g. bipolar disorders, binge-eating disorder, and attention-deficit hyperactivity disorder) are classified elsewhere in the DSM. ICD-NOS includes compulsive sexual behaviours, compulsive buying or shopping, problematic internet use, and compulsive skin picking [1]. Other psychiatric disorders or behaviours that share features of ICDs have been reported to occur in Parkinson's disease (PD) in the context of dopamine replacement therapy (DRT). For instance, with excessive use of DRT, patients have been reported to develop (hypo)mania, a mood disorder that can imply excessive involvement in pleasurable activities that have a high potential for painful consequences. In addition, obsessive–compulsive disorder, an anxiety disorder characterized by the repetition of nonharmful behaviours to reduce anxiety, may occur at an increased frequency in PD, although it has not been reported in association with DRT. Punding and walkabout are characterized by repetitive behaviours and poor impulse control, but the behaviours are typically nonpleasurable or low in risk–reward characteristics when compared with ICD behaviours [2]. Thus, ICDs may represent the severe end of a spectrum of behavioural disturbances in PD that are characterized by poorly or uncontrolled repetitive behaviours [3]. Another compulsive disturbance is represented by the dopamine dysregulation syndrome (DDS), which is characterized by the use of dopaminergic drugs in doses excessive to those required to treat motor symptoms despite the development of disabling dyskinesias [4]. The clinical characteristics of these patients meet accepted criteria for addiction: compulsive drug taking in excess of clinical requirements; intoxication similar to that seen with drugs such as cocaine and characterized by hypomania and impulsivity; persistent use despite social and personal difficulties caused by the drugs; withdrawal symptoms such as dysphoria and anxiety following dosage reductions; and hoarding the drug or obtaining prescriptions from different physicians.

The core features of ICDs include repetitive or compulsive engagement in a behaviour despite adverse consequences, diminished control over the problematic behaviour, an appetitive urge or craving state prior to engagement in the problematic behaviour, and a hedonic quality during the performance of the problematic behaviour. ICDs share a conceptual resemblance to drug addiction in that individuals pursue an activity in a compulsive manner despite harmful consequences, in particular the development of tolerance, the negative effect of withdrawal, repeated unsuccessful attempts to cut back or stop, and finally impairment in major areas of life functioning [5, 6, 7, 8].