Hypersexuality in Parkinson's Disease: Systematic Review and Report of 7 New Cases

Hypersexuality in neurological disorders: A systematic review

BACKGROUND

Hypersexuality (HS) accompanying neurological conditions remains poorly characterized despite profound psychosocial impacts. Objective We aimed to systematically review the literature on HS in patients with neurological disorders. Study selection and analysis We conducted a systematic review to identify studies that reported HS in neurological disorders. HS was defined as a condition characterized by excessive and persistent preoccupation with sexual thoughts, urges, and behaviors that cause significant distress or impairment in personal, social, or occupational functioning. Data on demographics, assessment techniques, associated elements, phenotypic manifestations, and management strategies were also extracted. Findings The final analysis included 79 studies on HS, encompassing 32 662 patients across 81 cohorts with neurological disorders. Parkinson's disease was the most frequently studied condition (55.6%), followed by various types of dementia (12.7%). Questionnaires were the most common assessment approach for evaluating HS, although the techniques varied substantially. Alterations in the dopaminergic pathways have emerged as contributing mechanisms based on the effects of medication cessation. However, standardized treatment protocols still need to be improved, with significant heterogeneity in documented approaches. Critical deficiencies include risks of selection bias in participant sampling, uncontrolled residual confounding factors, and lack of blinded evaluations of reported outcomes. Conclusions and clinical implications Despite growth in the last decade, research on HS remains limited across neurological conditions, with lingering quality and methodological standardization deficits. Key priorities include advancing assessment tools, elucidating the underlying neurobiology, and formulating management guidelines.

PROSPERO REGISTRATION NUMBER

CRD42017036478.

Contributory Factors to Caregiver Burden in Parkinson's Disease

Background

Although there is growing recognition of the relevancy of informal caregivers there is scarce information on the contributory factors of caregiver burden in Parkinson's Disease (PD).

Objective

To identify the main associated factors to caregivers' burden in people caring for a person with PD.

Methods

We analyzed the data set from a multinational online survey the Parkinson's real-world impact assesSMent (PRISM) focusing on medication use, comorbidities, health-related quality of life, relationship changes and the use of healthcare and supportive care resources by people with PD and their carers. Structured questionnaires including the Parkinson's disease quality of life questionnaire (PDQ-39), non-motor symptoms questionnaire (NMSQuest) and the Questionnaire for impulsive-compulsive disorder in Parkinson's disease (QUIP) were applied. Caregiver burden was assessed by the Zarit Burden Interview (ZBI).

Results

In a cohort of 245 dyads (patient and respective caregiver), caregivers reported a mild to moderate burden. Carers' perception of PD impact in partnership, financial burden, hours of care, patient's age, hypersexuality and health-related quality of life (HRQoL) were found to be significant contributory factors to caregiver burden. Taken together these variables explained 66.8% of the variance in the Interpretation of the ZBI total score.

Conclusions

Caring for a person with PD entails substantial burden, particularly when the caregiver perceives greater changes in partnership dynamics, dedicates more time to caregiving tasks, has financial burden, and when the patient is older, reports worst HRQoL and has sexual compulsive urges.

The Concept of "Hypersexuality" in the Boundary between Physiological and Pathological Sexuality

INTRODUCTION

The concept of hypersexuality belongs to modern parlance, according to a predominantly clinical meaning, and is understood as a psychological and behavioural alteration as a result of which sexually motivated stimuli are sought in inappropriate ways and often experienced in a way that is not completely satisfactory.

METHODS

Literature up to February 2023 was reviewed, with 25 searches selected.

RESULTS

Forty-two articles were included in the review.

CONCLUSION

Hypersexuality is a potentially clinically relevant condition consisting of one or more dysfunctional and pathological behaviours of one's sexual sphere and graded according to the severity of impairment of subjective acting out; for this reason, the Perrotta Hypersexuality Global Spectrum of Gradation (PH-GSS) is suggested, which distinguishes high-functioning forms (pro-active and dynamic hypersexuality) from those of attenuated and corrupted functioning (dysfunctional and pathological hypersexuality of grades I and II). Future research is hoped to address the practical needs of this condition, such as the exact etiopathology, the role of oxytocin in dopaminergic hypotheses (and its ability to attenuate the symptomatology suffered by the patient in terms of manic drive), the best structural and functional personality framing of the subject, and the appropriate therapy to pursue.

Sex Differences in Motor and Non-Motor Symptoms among Spanish Patients with Parkinson's Disease

BACKGROUND AND OBJECTIVE

Sex plays a role in Parkinson's disease (PD) mechanisms. We analyzed sex difference manifestations among Spanish patients with PD.

PATIENTS AND METHODS

PD patients who were recruited from the Spanish cohort COPPADIS from January 2016 to November 2017 were included. A cross-sectional and a two-year follow-up analysis were conducted. Univariate analyses and general linear model repeated measure were used.

RESULTS

At baseline, data from 681 PD patients (mean age 62.54 ± 8.93) fit the criteria for analysis. Of them, 410 (60.2%) were males and 271 (39.8%) females. There were no differences between the groups in mean age (62.36 ± 8.73 vs. 62.8 ± 9.24; p = 0.297) or in the time from symptoms onset (5.66 ± 4.65 vs. 5.21 ± 4.11; p = 0.259). Symptoms such as depression (p < 0.0001), fatigue (p < 0.0001), and pain (p < 0.00001) were more frequent and/or severe in females, whereas other symptoms such as hypomimia (p < 0.0001), speech problems (p < 0.0001), rigidity (p < 0.0001), and hypersexuality (p < 0.0001) were more noted in males. Women received a lower levodopa equivalent daily dose (p = 0.002). Perception of quality of life was generally worse in females (PDQ-39, p = 0.002; EUROHIS-QOL8, p = 0.009). After the two-year follow-up, the NMS burden (Non-Motor Symptoms Scale total score) increased more significantly in males (p = 0.012) but the functional capacity (Schwab and England Activities of Daily Living Scale) was more impaired in females (p = 0.001).

CONCLUSION

The present study demonstrates that there are important sex differences in PD. Long-term prospective comparative studies are needed.

Couples facing the “honeymoon period” of Parkinson's disease: A qualitative study of dyadic functioning

INTRODUCTION

The public health issue of the Parkinson's disease (PD) has led to a great deal of research that has highlighted the individual challenges faced by the person with the Parkinson's disease (PwPD) and the caregiving spouse. Few studies, however, have sought to understand the functioning of couples facing PD, by differentiating each stage, each of which has its own issues. In particular, the "honeymoon period", characterized by a symptomatic respite allowed by the effectiveness of treatments for motor symptoms, has been poorly documented, especially at the dyadic level.

DESIGN AND METHOD

This qualitative study, based on Interpretative Phenomenological Analysis, aimed to understand the experience of couples and their functioning at this stage. Fifteen couples participated in separate semi-structured interviews for each partner. The analyses highlighted four dyadic dynamics, which call into question the relevance of the term "honeymoon" to describe the experience of couples.

RESULTS

While some couples appear to adjust by means of flexible functioning and a positive reinterpretation of this experience, other dyads oscillate between rigid hyperprotection in the face of perceived distress or a vicious circle of control/avoidance and, in some cases, gradually slipping towards the erosion of the relationship.

DISCUSSION

These results show that the relational difficulties suffered by partners at this stage should be taken into account as soon as possible after the diagnosis. Strengthening the communication and the togetherness between partners, as well as working on dyadic emotional regulation, are particularly relevant options for these couples.

The impact of nonmotor symptom burden on sexual function

Sexual dysfunction (SD) is defined as a combination of reduction in libido, and problems with a person's ability to have sex. It is a frequent but neglected and poorly recognized nonmotor symptom (NMS) in Parkinson's disease (PD) which correlates with reduced quality of life (QoL). Hypersexuality forms another spectrum of SD and is an impulse control disorder (ICD) of behavior, which also affects the sexual desires of people with Parkinson's (PwP) and impacts their partner, family, and QoL. NMS occur in various forms and represents a range of symptoms, from cognitive dysfunction to pain and SD, and this chapter explores the relationship of comorbid NMS with SD and also how NMS, motor symptoms, and hypersexuality experienced by patients may impact sexual function in people with Parkinson's (PwP).

Impulse control disorders, dopamine dysregulation syndrome and sex dysfunction in Parkinson's disease

Hypersexuality (HS), characterized by an aberrant, compulsive and inappropriate sexual drive, is an underreported and undermanaged complication of the treatment with dopamine agonists in patients with Parkinson's disease (PD). HS is part of the spectrum of impulse control disorders (ICDs). The failure to control these addictive behaviors is distressing for the patient and it is associated with important consequences. Reports of the prevalence of HS showed different results, due to the lack of standardized diagnostic criteria, but also due to the embarrassment or guilt feelings that patients experience regarding their sexual behaviors. Overall, it is considered that HS may occur in 1.92-22.8% of PD patients and the main risk factors involved could be male sex and genetic susceptibility. The pathophysiology of HS is unknown, but several degenerative mechanisms were proposed, involving dopaminergic, serotoninergic and noradrenergic pathways in cerebral regions responsive for planning and rewarding. There are no standardized tools for the assessment of HS in PD patients; however, several scales and questionnaires were developed with the aim of screening and rating the severity of ICDs, including HS. The management of HS is challenging. Discontinuation or reducing the dopaminergic treatment was effective in some cases, but it might lead to worsening of the motor function. A multidisciplinary approach is mandatory to manage the other associated aspects, such as psychological and social consequences of HS.

The pathophysiology of sexual dysfunction in Parkinson's disease: An overview

Sexual dysfunction is a common, poorly recognized, poorly discussed (often because of cultural perceptions and sensitivities), bothersome and neglected aspect of the range of non-motor symptoms of Parkinson's disease (PD). The spectrum of sexual dysfunction in PD ranges from hyposexuality-based disturbances to hypersexuality-dominated behaviors in the context of drug-induced impulse control disorder. The pathophysiological mechanisms underlying PD-related sexual dysfunction, specifically for hyposexual disorders, are thus heterogeneous and still not fully understood. However, central and peripheral neural mechanisms secondary to the hallmark pathological alterations of the disease (alpha-synuclein deposition and nigrostriatal degeneration) and to the associated network and neurotransmitter dysfunctions, together with the effects of dopaminergic therapies, seem to play an important role in the development of sexual disturbances. In this chapter, we therefore review the neuroanatomical and neurophysiological basis of sexual function in humans, and we provide insights on the pathophysiological mechanisms of hyposexuality and hypersexuality in PD.

Exploring sexual dysfunction in care homes

Sexual needs and sexuality in older adults continues to be a neglected area of clinical intervention, particularly in longer term care settings. This is often due to older adults in long term care beds presenting with increased frailty, and often with significant neurocognitive disorders, making it difficult for care staff to evaluate the capacity of an older adult resident to participate in sexual activities or a sexual relationship. Talking about sexuality, intimacy and sexual health can be embarrassing at any age and sex is often still considered taboo for people who live in care homes. The World Health Organization recently declared that sexual health is a central aspect of life and that each individual has the right to love and be loved, to receive appropriate information and treatment, and to enable intimate relationships and personal control over sexual behavior. This chapter explores sexual behaviors, and barriers to this, in later life, and focuses on the sexual behavior of care home residents with Parkinson's disease. Reasons for sexual dysfunction, potential age-related changes to sexual functioning, along with issues such as changes to body image, intimacy and hyper sexuality, are examined for people with Parkinson's disease. Recommendations for practice are given, and acknowledge that older people may still want to be sexually active or intimate is the first step to addressing the issues and overcoming any barriers.

Sexual Dysfunctions in Parkinson’s Disease and Their Influence on Partnership—Data of the PRISM Study

Background: Sexual dysfunctions (SD) are common but underreported in Parkinson’s disease (PD) and have negative impacts on the quality of life (QoL) and partnership. Methods: We analyzed the data set from the PRISM study for demographics of SD and their influence on quality of life and partnership. Results: 449/861 (52.1%) PD patients reported SD, with male patients being affected more often and having a longer course of disease. The most common SD in men was erectile dysfunction (ED) (n = 152), while women’s most frequent complaints were orgasm dysfunction (n = 84) and reduced libido (n = 81). Hypersexual SDs were reported significantly more often by men. Spousal caregivers of patients reporting inability to relax and enjoy sex and reduced libido indicated a negative influence on the relationship in general. Negative effects on the sexual relationship were reported significantly more often for patients with ED, difficulties with sexual arousal, inability to relax and enjoy sex, and reduced libido. Hypersexual dysfunctions showed no effect on the relationship. Conclusion: SD is a common but underreported problem in the treatment of patients with PD. Due to the negative influence on the relationship and QoL of patients and caregivers, SD should be assessed routinely.

Treatment and Management of Sexual Disinhibition in Elderly Patients With Neurocognitive Disorders

Sexual disinhibition is uncommon but challenging symptom to address in elderly patients with neurocognitive disorders. Due to the lack of large-scale studies, there is no gold standard treatment for sexual disinhibition, and treatment is largely left up to the discretion of the provider based on the severity and onset of the patient's symptoms. A review was conducted to investigate the non-pharmacological and pharmacological interventions for treating this condition. Articles that discussed treatments were screened for the type of treatment and possible side effects of medication if applicable. Thorough patient history should be taken prior to starting any drug therapy to rule out possible behavioral changes due to an existing medication side effect, delirium, or past mental or sexual health history. Non-pharmacological treatment has been generally recommended as first-line therapy over pharmacological treatment. Distraction/diversion of the patient when inappropriate sexual behaviors occur was the most common non-pharmacological intervention. Antidepressants were generally recommended as the first line of pharmacological treatment after attempting all possible non-pharmacological interventions. Several other categories of interventions are discussed as well in addition to the ethical implications of treating a patient for this condition.

Sexual Disorders and Quality of Life in Parkinson's Disease

Introduction

Sexual disorders are the most neglected nonmotor symptoms in Parkinson's disease (PD). Although doctors seek greater priority to motor manifestations, which are the basis for the diagnosis of PD, the nonmotor symptoms deserve to be highlighted as much as the motor problems because of their strong presence and discomfort in the patients, causing the important impairment in the quality of life (QoL) of the individual with PD.

Aim

Provide the prevalence of sexual disorders among patients with PD and alert the medical profession to investigate and be familiar with problems related to QoL and sexual disorders in PD.

Methods

This is a large literature review on sexual disorders in PD and impaired QoL.

Main Outcome Measures

Sexual disorders in PD and prevalence between genders have been described in epidemiological studies. Neuroanatomy, pathophysiology, risk factors, QoL, and etiologies were reviewed.

Results

The estimate of the prevalence of sexual dysfunction in the form of compulsive sexual behavior in PD is higher in men by 5.2% than in women by 0.5%. This diagnosis is a determinant of intense and persistent suffering and is related to several health problems of a social, economic, personal, family, psychological, and occupational nature, which can even culminate in sexual abuse. It is most commonly associated with the use of drugs commonly used in PD therapy in 98.1% of cases. In addition to this serious public health problem, another common condition of sexual dysfunction occur with the decreased libido by loss of the neurotransmitter dopamine proper of the pathophysiology of PD.

Conclusion

The presence of sexual disorders in PD should be tracked and monitored because of its harmful consequences, whether due to increased sexual behavior or associated psychological distress, as well as the impacts on QoL. Early recognition and adequate treatment of PD in its fullness and richness of associated symptoms are essential for improving QoL.

Santa Rosa Malcher CM, Roberto da Silva Gonçalves Oliveira K, Fernandes Caldato MC, et al. Sexual Disorders and Quality of Life in Parkinson's Disease. Sex Med 2021;9:100280.

Erectile dysfunction in common neurological conditions: A narrative review

Neurogenic erectile dysfunction (NED) can be defined as the inability to achieve or maintain an erection due to central or peripheral neurologic disease. Neurologic diseases can also affect the physical ability and psychological status of the patient. All these factors may lead to a primary or secondary NED. Medication history plays an important role since there are many drugs commonly used in neurologic patients that can lead to ED. The assessment of NED in these patients is generally evolving with the application of evoked potentials technology in the test of somatic and autonomic nerves, and functional magnetic resonance imaging. With the electrophysiological examinations, neurogenic causes can be determined. These tools allow to categorize neurologic lesion and assess the patient prognosis. The first-line treatment for NED is phosphodiesterase inhibitors. Second-line treatments include intracavernous and intraurethral vasoactive injections. Third-line treatments are penile prostheses. The efficacy and safety of each treatment modality depend on the specific neurologic condition. This review discusses the physiology, pathophysiology, diagnosis, and treatment of ED in multiple peripheral and central neurologic conditions, as well as for future research.

The experiences of carers looking after people with Parkinson's disease who exhibit impulsive and compulsive behaviours: An exploratory qualitative study

AIM

To understand the experiences of carers who were confronted by the development of impulsive and compulsive behaviours.

BACKGROUND

Impulsive and compulsive behaviours (ICBs) are a serious complication in Parkinson's disease (PD) strongly associated with dopamine replacement therapy used to treat patients. These behaviours comprise abnormal activities such as pathological gambling, binge eating, compulsive shopping and hypersexuality. These behaviours place a considerable burden on patients and on their carers and families.

DESIGN

An exploratory qualitative study.

METHODS

Using a convenience sampling approach, 13 carers were recruited to participate in semi-structured interviews. Interviews were conducted over the telephone. Verbatim transcripts were analysed using a thematic analysis approach. COREQ guidelines were adhered to in the reporting of this study.

RESULTS

Five main themes were identified: (a) realisation-developing awareness of ICB symptoms and their causes; (b) reacting-confronting and attempts to manage ICBs; (c) reaching out-help-seeking and selective disclosure; (d) reframing-shifting perspectives on ICBs over time; and (e) resignation-impact on relationships and facing the future.

CONCLUSIONS

The profound impact of ICBs on quality of life, relationships and economic stability was clear in the carers' accounts. Possible avenues for future clinical research are suggested.

RELEVANCE TO CLINICAL PRACTICE

The potentially devastating effects of ICBs provide a strong imperative for nurses and other health professionals to ensure that close monitoring for symptom development together with patient education is always part of practice.

A Comparative Study of the Behavioral Profile of the Behavioral Variant of Frontotemporal Dementia and Parkinson's Disease Dementia

BACKGROUND

Executive dysfunction is the common thread between pure cortical dementia like the behavioral variant of frontotemporal dementia (bvFTD) and subcortical dementia like Parkinson's disease dementia (PDD). Although there are clinical and cognitive features to differentiate cortical and subcortical dementia, the behavioral symptoms differentiating these 2 conditions are still not well known.

OBJECTIVE

To evaluate the behavioral profile of bvFTD and PDD and compare them to find out which behavioral symptoms can differentiate between the two.

METHODS

Twenty consecutive patients with bvFTD (>1 year after diagnosis) and 20 PDD patients were recruited according to standard diagnostic criteria. Behavioral symptoms were collected from the reliable caregiver by means of a set of questionnaires and then compared between the 2 groups.

RESULTS

bvFTD patients had more severe disease and more behavioral symptoms than PDD. bvFTD patients were different from PDD patients due to their significantly greater: loss of basic emotion (p < 0.001, odds ratio [OR] 44.33), loss of awareness of pain (p < 0.001, OR 44.33), disinhibition (p < 0.001, OR 35.29), utilization phenomenon (p = 0.008, OR 22.78), loss of taste discrimination (p < 0.001, OR 17), neglect of hygiene (p = 0.001, OR 13.22), loss of embarrassment (p = 0.003, OR 10.52), wandering (p = 0.004, OR 9.33), pacing (p = 0.014, OR 9), selfishness (p = 0.014, OR 9), increased smoking (p = 0.014, OR 9), increased alcohol consumption (p = 0.031, OR 7.36), social avoidance (p = 0.012, OR 6.93), mutism (p = 0.041, OR 5.67), and failure to recognize objects (p = 0.027, OR 4.33). The bvFTD patients were also significantly less suspicious (p = 0.001, OR 0.0295), less inclined to have a false belief that people were in their home (p = 0.014, OR 0.11) and had fewer visual illusions/hallucinations (p = 0.004, OR 0.107) than PDD patients.

CONCLUSION

Behavioral symptoms are helpful to distinguish bvFTD from PDD, and thus also cortical dementia with frontal-lobe dysfunction from subcortical dementia.

The Impact of Deep Brain Stimulation on the Sexual Function of Patients With Parkinson's Disease

BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is used in the treatment of advanced Parkinson's disease (PD) with well-established benefits over motor complications. However, few studies addressing the impact of DBS on nonmotor dimensions such as sexual function have been conducted. This study aims to determine the effect of DBS-STN on the sexual activity of patients with PD and to establish predictive factors for sexual function decline after surgery.

MATERIALS AND METHODS

Twenty-one patients with PD submitted to DBS-STN were compared with 19 eligible surgery candidates. Clinical measures included disease progression (Hoehn and Yahr scale), sexual function evaluation (Female Sexual Function Index and International Index of Erectile Function), severity of depressive symptoms (Beck Depressive Inventory-II), motor symptoms (Movement Disorders Society-Unified Parkinson's Disease Rating Scale Part III), and quality of life (39-item Parkinson's Disease Questionnaire). The primary outcomes were the development of sexual dysfunction in women and erectile dysfunction in men. Regression analysis was performed to outline risk factors for developing sexual function deterioration.

RESULTS

Erectile dysfunction was present in 83.3% of men and sexual dysfunction in 77.8% of women treated with DBS-STN. Women with sexual dysfunction had higher emotional well-being 39-item Parkinson's Disease Questionnaire scores (P=0.017) and a higher prevalence of cardiovascular diseases (P=0.012) comparing with women without sexual dysfunction. Age was an independent predictive factor for developing erectile dysfunction in men (relative risk=1.26; P=0.033) and sexual dysfunction in women (relative risk =1.30; P=0.039), regardless of DBS-STN submission.

CONCLUSIONS

Sexual function in both sexes of patients with PD does not seem to be influenced by DBS-STN itself, but by psychological and clinical features.

Stimulation-induced side effects after deep brain stimulation - a systematic review

OBJECTIVE

Deep brain stimulation (DBS) was approved by Food and Drug Administration for Parkinson's disease, essential tremor, primary generalised or segmental dystonia and obsessive-compulsive disorder (OCD) treatment. The exact mechanism of DBS remains unclear which causes side effects. The aim of this review was to assess variables causing stimulation-induced chronic psychiatric/personality-changing side effects.

METHODS

The analysis of scientific database (PubMed, Cochrane Library, EMBASE) was conducted. The included articles had to be research study or case report and DBS to be conducted in therapeutic purposes. The researches with mental disorders in patients' medical histories were excluded.

RESULTS

Seventeen articles were used in the review. In the group of movement disorders the characteristic of side effects was strongly related to the placement of the electrode implantation. Tiredness/fatigue was correlated with DBS in thalamus. Implantations in subthalamic nucleus were mostly followed by affective side effects such as depression or suicide. The higher voltage of electrode was connected with more severe depression after implantation. The analysis of affective disorder contained only three articles - two about OCD and one about depression. Forgetfulness and word-finding problems as activities connected with cognition may be an inevitable side effect if obsessive thoughts are to be inhibited.

CONCLUSION

DBS of subthalamic nucleus should be seen as the most hazardous place of implantation. As a result there is a strong need of 'gold standards' based on the connectivity research and closer cooperation of scientists and clinicians.

Neurocognitive correlates of medication-induced addictive behaviours in Parkinson's disease: A systematic review

Dopaminergic medication can induce severe addictive behaviours (e.g., pathological gambling) in susceptible Parkinson's disease (PD) patients. It is still unknown which particular neurocognitive processes become exacerbated or dysfunctional in PD patients with addictive behaviours. We sought to systematically review the relevant literature to identity potential neurocognitive correlates of medication-induced addictive behaviours in PD. We framed our review around neurocognitive processes central to four dominant accounts of substance addiction: 'aberrant learning', 'incentive sensitization', 'impulsivity to compulsivity' and 'impaired response inhibition and salience attribution'. Searches of the PubMed and Scopus databases were completed on June 23, 2017. To be included, studies were required to involve: (a) medicated PD patients, without a history of deep brain stimulation, with and without addictive behaviours; (b) a reward-related or decision-making task; and (c) statistical comparison of addictive and non-addictive groups' 'on' medication performance on the task(s). Studies were summarised qualitatively with statistically significant (p<.05) group differences and effect sizes (Cohen's d) highlighted. 35 studies were included. Findings showed that the extant literature is highly heterogeneous. The domains of reward and punishment learning, reflection impulsivity and disadvantageous decision-making exemplify this. More homogeneity exists in domains in which (a) neurocognitive dysfunction is not apparent (motor control, cognitive/attentional flexibility and cognitive control) or (b) typical neurocognitive processes appear exacerbated by medication (reward motivation and choice impulsivity). Future large-scale neurocognitive studies are still required to develop our scientific understanding of addictive behaviours in PD and aid their clinical treatment and prediction.