The relationship between impulsivity and impulse control disorders in Parkinson's disease

Frequency of Impulsive-Compulsive Behavior and Associated Psychological Factors in Parkinson's Disease: Lack of Control or Too Much of It?

Background and Objectives: Impulse Control Disorders (ICDs) including pathological gambling, hypersexuality, compulsive eating, compulsive buying, and other related behaviors are well-known distinct non-motor symptoms in Parkinson's Disease (PD). Some large-scale studies present a prevalence of at least 10%, however, there are other reports providing much higher rates. The majority of the conducted studies investigating ICDs focus mainly on pharmacological factors, however, from a psychological perspective, there is yet enough room for investigation. In order to address the above issues, we designed a two-part study. Materials and Methods: First, we aimed to identify the incidence of ICD and related behaviors in a cohort of 892 Greek PD patients. Second, we administered a comprehensive battery of psychometric tools to assess psychological factors such as personality dimensions, quality of life, defenses, coherence, and resilience as well as to screen general cognitive capacity in PD patients with ICD manifestations. Results: With regard to the first part, we identified ICD manifestations in 12.4% of the patients. Preliminary findings from the second part indicate elevated activity, rather than impulsivity, as well as interrelations between several variables, including measures of activity, coping mechanisms, and quality of life. Conclusions: We present a working hypothesis for the contribution of high activity channeled to specific behavioral patterns through specific coping mechanisms, concerning the emergence of ICDs and related behaviors in PD, and further stress the importance of compulsivity rather than impulsivity in this process.

Impulsivity Traits in Parkinson's Disease: A Systematic Review and Meta-Analysis

Background

In Parkinson's disease (PD), impulsivity as a personality trait may be linked to the risk of developing impulse control disorders (ICDs) during dopaminergic therapy. However, studies evaluating differences in trait impulsivity between patients with PD and healthy controls or between patients with PD with and without ICDs reported partly inconsistent findings.

Objectives

We conducted a systematic review and meta-analysis (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) of studies comparing Barratt Impulsiveness Scale (BIS-11) scores between patients with PD and healthy controls and between patients with PD with and without ICDs.

Methods

Eligible studies were identified through a systematic search in 3 databases. Mean differences with 95% confidence intervals (CIs) for BIS-11 total and subscale scores were separately calculated for studies comparing patients with PD and healthy controls and patients with PD with and without ICDs. Meta-regressions were performed to explore sources of heterogeneity (percentage of men, age, disease duration, and levodopa equivalent daily dose).

Results

A total of 40 studies were included in the quantitative analyses. BIS-11 total scores were significantly higher in patients with PD compared with healthy controls (mean difference 2.43; 95% CI, 1.03, 3.83), and in patients with PD with active ICDs compared with patients without ICDs (6.62; 95% CI, 5.01, 8.23). No significant moderators emerged by meta-regression analyses.

Conclusions

The present meta-analysis supports that impulsivity, as a personality trait, may characterize patients with PD, even in the absence of ICDs. Moreover, these data corroborate findings of clinical studies reporting higher levels of trait impulsivity in PD patients with ICDs compared with patients without ICDs.

Quality of life implications for elevated trait impulsivity in people with Parkinson's disease

BACKGROUND

Several non-motor features of Parkinson's disease (PD) are known to adversely affect patient health-related quality of life (HRQL). However, the specific impact of neuropsychiatric complications, such as impulsive behaviour, is yet to be elucidated.

OBJECTIVES

The present cross-sectional, observational study aimed to investigate the effects of heightened trait impulsivity on HRQL in individuals with PD.

METHODS

A total of 322 people with idiopathic PD were sequentially recruited from Movement Disorder clinics across Australia. Trait impulsivity in patients was determined by Barratt's Impulsiveness Scale Version 11 (BIS-11), and grouped into tertiles (low, medium, and high). Patient HRQL was determined by the 39-item Parkinson's Disease Questionnaire (PDQ-39), complemented by the Cambridge Behavioural Inventory-Revised (CBI-R) indicating caregivers' perception of patient HRQL.

RESULTS

When total BIS-11 scores were grouped into tertiles, patient perceived and caregiver-perceived HRQL were 1.7-fold (p < .001) and 2.2-fold (p < .001) worse in the high BIS-11 group when compared to patients in the low group. Univariate analysis revealed significant associations between second-order attentional (p < .001) and non-planning (p < .001) impulsivity domains with PDQ-39 scores. When controlling for confounding demographic and clinical variables, a multivariate linear regression model revealed second-order attentional impulsivity was independently predictive of poor patient perceived HRQL (p < .001).

CONCLUSION

These findings suggest that increasing trait impulsivity is significantly associated with patient perceived HRQL in PD. Improved knowledge and recognition of subclinical impulsivity may guide clinicians' treatment and reduce disease burden for patients experiencing PD symptoms.

Performance on the balloon analogue risk task and anticipatory response inhibition task is associated with severity of impulse control behaviours in people with Parkinson's disease

Dopamine agonist medication is one of the largest risk factors for development of problematic impulse control behaviours (ICBs) in people with Parkinson's disease. The present study investigated the potential of dopamine gene profiling and individual performance on impulse control tasks to explain ICB severity. Clinical, genetic and task performance data were entered into a mixed-effects linear regression model for people with Parkinson's disease taking (n = 50) or not taking (n = 25) dopamine agonist medication. Severity of ICBs was captured via the Questionnaire for Impulsive-compulsive disorders in Parkinson's disease Rating Scale. A cumulative dopamine genetic risk score (DGRS) was calculated for each participant from variance in five dopamine-regulating genes. Objective measures of impulsive action and impulsive choice were measured on the Anticipatory Response Inhibition Task and Balloon Analogue Risk Task, respectively. For participants on dopamine agonist medication, task performance reflecting greater impulsive choice (p = 0.014), and to a trend level greater impulsive action (p = 0.056), as well as a longer history of DA medication (p < 0.001) all predicted increased ICB severity. DGRS however, did not predict ICB severity (p = 0.708). No variables could explain ICB severity in the non-agonist group. Our task-derived measures of impulse control have the potential to predict ICB severity in people with Parkinson's and warrant further investigation to determine whether they can be used to monitor ICB changes over time. The DGRS appears better suited to predicting the incidence, rather than severity, of ICBs on agonist medication.

Parkinson's disease and iatrogenic impulsive-compulsive behaviors: A case/non-case study to build a complete model of individual vulnerability

BACKGROUND AND AIMS

Parkinson's disease (PD) is one of the most prevalent neurodegenerative diseases. First-line medications consist of drugs that act by counteracting dopamine deficiency in the basal ganglia. Unfortunately, iatrogenic impulsive-compulsive behaviors (ICBs) can occur in up to 20% of PD patients over the course of their illness. ICBs must be considered multifactorial disorders that reflect the interactions of the medication with an individual's vulnerability and the underlying neurobiology of PD. We aimed to explore the predictive genetic, psychopathological and neurological factors involved in the development of ICBs in PD patients by building a complete model of individual vulnerability.

METHODS

The PARKADD study was a case/non-case study. A total of 225 patients were enrolled ("ICB" group, N = 75; "no ICB" group, N = 150), and 163 agreed to provide saliva samples for genetic analysis. Sociodemographic, neurological and psychiatric characteristics were assessed, and genotyping for the characterization of polymorphisms related to dopaminergic and opioid systems was performed.

RESULTS

Factors associated with "ICBs" were younger age of PD onset, personal history of ICB prior to PD onset and higher scores on the urgency and sensation seeking facets of impulsivity. No gene variant was significantly associated, but the association with the opioid receptor mu 1 (OPRM1) rs1799971 polymorphism was close to significance.

DISCUSSION AND CONCLUSIONS

The influence of gene-environment interactions probably exists, and additional studies are needed to decipher the possible role of the opioid system in the development of ICBs in PD patients.

A single-arm open-label pilot study of brief mindfulness meditation to control impulsivity in Parkinson’s disease

Background

Impulse control disorders are detrimental neuropsychiatric symptoms of Parkinson’s disease. Increased impulsivity is a predisposing factor for impulse control disorders and should therefore be controlled. Recently, mindfulness meditation as a non-drug therapy has been reported to be useful in improving neuropsychiatric symptoms, such as impulsivity.

Methods

We performed a prospective single-arm, open-label pilot trial to investigate the effectiveness of mindfulness meditation to control impulsivity in patients with Parkinson’s disease (UMIN clinical trials registry: UMIN000037779).

Results

Twenty patients with Parkinson’s disease were enrolled in an 8-week mindfulness meditation program. As a primary outcome, we investigated whether the score of the Barratt Impulsiveness Scale (BIS-11) was significantly reduced after the intervention. As an exploratory examination, functional connectivity changes were also assessed by resting-state functional magnetic resonance imaging. After the intervention, the BIS-11 score was decreased from 59.5 [55.6, 63.3] (mean [95% confidence interval]) to 55.2 [50.3, 60.1] (ΔBIS-11: -4.2, [-7.5, -0.9]). Functional connectivity was increased in the default mode network (DMN) at a cluster including the precuneus, posterior cingulate gyrus, and left posterior lobe (false discovery rate-adjusted p [FDR-p] = 0.046) and in the right frontoparietal network (FPN) at the medial frontal lobe (FDR-p = 0.039).

Conclusions

This open-label, single-arm pilot study provided preliminary data for mindfulness meditation to control the impulsivity of patients with PD. A brief mindfulness meditation program may be effective in controlling impulsivity in PD and may change the functional connectivity of the DMN and right FPN.

Impulsivity traits and awareness of motor intention in Parkinson's disease: a proof-of-concept study

INTRODUCTION

In patients with Parkinson's disease (PD), impulsivity is still a matter of investigation. It has been hypothesized that impulsive personality traits may favour impulse control disorder (ICD) onset during dopaminergic therapy. In healthy subjects, a relationship between the awareness of motor intention and impulsive personality traits assessed by the Barratt impulsivity scale (BIS-11) has been reported. The aim of this study was to evaluate the relationship between the awareness of voluntary action and impulsivity traits in PD.

METHODS

Twenty-eight PD patients (stages I-III on the Hoehn and Yahr scale) underwent an impulsivity trait assessment by the BIS-11 scale and a task based on the Libet's clock. Participants were requested to perform a self-initiated movement and report the time they first feel their intention to move (W-judgement) or the time of the actual movement (M-judgement).

RESULTS

In patients with higher BIS-11 scores, the time lag between the W-judgement and the actual movement was significantly lower than in patients with lower BIS-11. No difference emerged in the M-judgement.

CONCLUSION

Data suggest that also in PD patients, the impulsive personality trait is related to a "delayed" awareness of motor intention and therefore to a shorter interval to allow a conscious "veto" of the impending action. Characterization of the temporal profile of awareness of motor intention could prove useful in identifying PD patients at risk of developing ICDs during dopaminergic treatment.

Neurophysiological Correlates of Trait Impulsivity in Parkinson's Disease

Background

Impulsivity is common in people with Parkinson’s disease (PD), with many developing impulsive compulsive behavior disorders (ICB). Its pathophysiological basis remains unclear.

Objectives

We aimed to investigate local field potential (LFP) markers of trait impulsivity in PD and their relationship to ICB.

Methods

We recorded subthalamic nucleus (STN) LFPs in 23 PD patients undergoing deep brain stimulation implantation. Presence and severity of ICB were assessed by clinical interview and the Questionnaire for Impulsive-Compulsive Disorders in PD-Rating Scale (QUIP-RS), whereas trait impulsivity was estimated with the Barratt Impulsivity Scale (BIS-11). Recordings were obtained during the off dopaminergic states and the power spectrum of the subthalamic activity was analyzed using Fourier transform-based techniques. Assessment of each electrode contact localization was done to determine the topography of the oscillatory activity recorded.

Results

Patients with (n = 6) and without (n = 17) ICB had similar LFP spectra. A multiple regression model including QUIP-RS, BIS-11, and Unified PD Rating Scale-III scores as regressors showed a significant positive correlation between 8–13 Hz power and BIS-11 score. The correlation was mainly driven by the motor factor of the BIS-11, and was irrespective of the presence or absence of active ICB. Electrode contact pairs with the highest α power, which also correlated most strongly with BIS-11, tended to be more ventral than contact pairs with the highest beta power, which localize to the dorsolateral motor STN.

Conclusions

Our data suggest a link between α power and trait impulsivity in PD, irrespective of the presence and severity of ICB.

A pain-induced tonic hypodopaminergic state augments phasic dopamine release in the nucleus accumbens

Diseases and disorders such as Parkinson disease, schizophrenia, and chronic pain are characterized by altered mesolimbic dopaminergic neurotransmission. Dopamine release in the nucleus accumbens influences behavior through both tonic and phasic signaling. Tonic dopamine levels are hypothesized to inversely regulate phasic signals through dopamine D2 receptor feedback inhibition. We tested this hypothesis directly in the context of ongoing pain. Tonic and phasic dopamine signals were measured using fast-scan controlled-adsorption voltammetry and fast-scan cyclic voltammetry, respectively, in the nucleus accumbens shell of male rats with standardized levels of anesthesia. Application of capsaicin to the cornea produced a transient decrease in tonic dopamine levels. During the pain-induced hypodopaminergic state, electrically evoked phasic dopamine release was significantly increased when compared to baseline, evoked phasic release. A second application of capsaicin to the same eye had a lessened effect on tonic dopamine suggesting desensitization of TRPV1 channels in that eye. Capsaicin treatment in the alternate cornea, however, again produced coincident decreased dopaminergic tone and increased phasic dopamine release. These findings occurred independently of stimulus lateralization relative to the hemisphere of dopamine measurement. Our data show that (1) the mesolimbic dopamine circuit reliably encodes acute noxious stimuli; (2) ongoing pain produces decreases in dopaminergic tone; and (3) pain-induced decreases in tonic dopamine correspond to augmented evoked phasic dopamine release. Enhanced phasic dopamine neurotransmission resulting from salient stimuli may contribute to increased impulsivity and cognitive deficits often observed in conditions associated with decreased dopaminergic tone, including Parkinson disease and chronic pain.

Does the Country Make a Difference in Impulse Control Disorders? A Systematic Review

BACKGROUND

Impulse control disorders (ICDs) have an increased frequency in patients with Parkinson's disease (PD), mainly because of treatment with dopamine agonists (DA). Factors related with the country of origin (culture, economy, healthcare politics) may impact phenomenology.

OBJECTIVES

To explore phenomenology of ICDs depending on the country.

METHODS

A systematic review following PRISMA guidelines was performed using Pubmed database. Articles published up to 2018 in which the prevalence of ICDs was analyzed were selected.

RESULTS

Thirty-two studies from 22 countries worldwide were included. The highest prevalence of ICDs in each continent was found in UK (59%), USA (39.1%) and India (31.6%). Frequency of ICDs was higher in those studies with lower mean age, higher proportion of males, whenever a screening instrument was used and whenever prescription of DAs was more common. Prevalence of ICDs was higher in Western countries compared to Asian countries (20.8% vs. 12.8%, P < 0.001) as it was the proportion of patients treated with DAs (66% vs. 48.2%, P < 0.001). Hypersexuality was the most common ICD overall (up to 23.8%). The highest frequencies of compulsive buying and eating were found in Western countries. Gambling was less commonly diagnosed, but prevalence was relevant Japan (14%).

CONCLUSION

We observed a tendency towards a different ICD profile in different geographical areas, which may be attributable to socio-economical, cultural or political influences in the phenomenology of these disorders. Acknowledging these differences could help their early detection, which is critical for prognosis.

Impulse Control Disorders in Parkinson's Disease: Epidemiology, Pathogenesis and Therapeutic Strategies

Impulse control disorders (ICDs) in Parkinson's disease (PD) are aberrant behavior such as pathological gambling, hypersexuality, binge eating, and compulsive buying, which typically occur as a result of dopaminergic therapy. Numerous studies have focused on the broad spectrum of ICDs-related behaviors and their tremendous impact on patients and their family members. Recent advances have improved our understanding of ICDs. In this review, we discuss the epidemiology, pathogenesis and treatment of ICDs in the setting of PD.

Elevated Serum Ceruloplasmin Levels Are Associated with Higher Impulsivity in People with Parkinson's Disease

BACKGROUND

Heightened impulsivity has been reported in a subset of people with Parkinson's disease (PwP) and is considered a risk factor for the development of impulse control disorders (ICDs). However, at present, there are no recognised biochemical markers of heightened impulsivity.

OBJECTIVES

To determine if ceruloplasmin, a serum marker involved in the regulation of iron and copper homeostasis, is associated with trait impulsivity in PwP.

METHODS

The study measured serum ceruloplasmin and impulsivity using the Barratt Impulsiveness Scale (BIS-11) in an Australian cohort of 214 PwP. Multivariate general linear models (GLMs) were used to identify whether higher serum ceruloplasmin levels (>75th percentile) were significantly predictive of BIS-11 scores.

RESULTS

Serum ceruloplasmin was higher in females with PD (p < 0.001) and associated with MDS-UPDRS III, Hoehn and Yahr, and ACE-R scores (p < 0.05). When correcting for covariates, higher serum ceruloplasmin concentrations were associated with the 2nd order nonplanning impulsivity and with the 1st order self-control and cognitive complexity impulsivity domains.

CONCLUSIONS

Higher serum ceruloplasmin levels are independently associated with heightened nonplanning impulsivity in PwP. Thus, serum ceruloplasmin levels may have clinical utility as a marker for heightened impulsivity in PD.

Pavlovian bias in Parkinson's disease: an objective marker of impulsivity that modulates with deep brain stimulation

Impulsivity is a common symptom in Parkinson's disease (PD). Adaptive behavior is influenced by prepotent action-reward and inaction-avoid loss Pavlovian biases. We aimed to assess the hypothesis that impulsivity in PD is associated with Pavlovian bias, and to assess whether dopaminergic medications and deep brain stimulation (DBS) influence Pavlovian bias. A PD DBS cohort (N = 37) completed a reward-based Go/No-Go task and bias measures were calculated. This DBS cohort completed the task under three conditions: on-med/pre-DBS, off-med/off-DBS, and on-med/on-DBS. Participants also completed self-reported measures of impulsivity. Dopaminergic medication was associated with lower action-reward bias while DBS was associated with higher action-reward bias. Impulsivity was associated with higher action-reward bias but not inaction-avoid loss bias. We furthermore replicated this association in an independent, non-DBS PD cohort (N = 88). Overall we establish an objective behavioral marker of impulsivity and show that DBS affects impulsivity by amplifying automated responding. Our results point to the importance of reward rather than punishment avoidance in driving impulsive behaviors. This work provides insight into the pathophysiological underpinnings of impulsivity and especially medication and DBS-associated impulsivity in PD.

Dopamine and reward hypersensitivity in Parkinson's disease with impulse control disorder

Impulse control disorders in Parkinson's disease are common neuropsychiatric complications associated with dopamine replacement therapy. Some patients treated with dopamine agonists develop pathological behaviours, such as gambling, compulsive eating, shopping, or disinhibited sexual behaviours, which can have a severe impact on their lives and that of their families. In this study we investigated whether hypersensitivity to reward might contribute to these pathological behaviours and how this is influenced by dopaminergic medication. We asked participants to shift their gaze to a visual target as quickly as possible, in order to obtain reward. Critically, the reward incentive on offer varied over trials. Motivational effects were indexed by pupillometry and saccadic velocity, and patients were tested ON and OFF dopaminergic medication, allowing us to measure the effect of dopaminergic medication changes on reward sensitivity. Twenty-three Parkinson's disease patients with a history of impulse control disorders were compared to 26 patients without such behaviours, and 31 elderly healthy controls. Intriguingly, behavioural apathy was reported alongside impulsivity in the majority of patients with impulse control disorders. Individuals with impulse control disorders also exhibited heightened sensitivity to exogenous monetary rewards cues both ON and OFF (overnight withdrawal) dopamine medication, as indexed by pupillary dilation in anticipation of reward. Being OFF dopaminergic medication overnight did not modulate pupillary reward sensitivity in impulse control disorder patients, whereas in control patients reward sensitivity was significantly reduced when OFF dopamine. These effects were independent of cognitive impairment or total levodopa equivalent dose. Although dopamine agonist dose did modulate pupillary responses to reward, the pattern of results was replicated even when patients with impulse control disorders on dopamine agonists were excluded from the analysis. The findings suggest that hypersensitivity to rewards might be a contributing factor to the development of impulse control disorders in Parkinson's disease. However, there was no difference in reward sensitivity between patient groups when ON dopamine medication, suggesting that impulse control disorders may not emerge simply because of a direct effect of dopaminergic drug level on reward sensitivity. The pupillary reward sensitivity measure described here provides a means to differentiate, using a physiological measure, Parkinson's disease patients with impulse control disorder from those who do not experience such symptoms. Moreover, follow-up of control patients indicated that increased pupillary modulation by reward can be predictive of the risk of future emergence of impulse control disorders and may thereby provide the potential for early identification of patients who are more likely to develop these symptoms.

Increased large-scale inter-network connectivity in relation to impulsivity in Parkinson's disease

Impulsivity is a neuropsychiatric feature of Parkinson’s disease (PD). We investigated the pathophysiology of impulsivity in PD using resting-state functional magnetic resonance imaging (rs-fMRI). We investigated 45 patients with idiopathic PD and 21 healthy controls. Based on Barratt Impulsiveness Scale (BIS-11) score, PD patients were classified as higher (PD-HI) or lower impulsivity (PD-LI). Functional connectivity (FC) between various large-scale brain networks were analysed using the CONN toolbox. FC between the right frontoparietal network (FPN) and medial visual network (MVN) was significantly higher in PD-HI patients than PD-LI patients (false discovery rate [FDR]-adjusted p = 0.0315). FC between the right FPN and MVN had a significant positive correlation with total BIS-11 score (FDR-adjusted p = 0.010) and the attentional impulsivity (FDR-adjusted p = 0.046) and non-planning impulsivity subscale scores (FDR-adjusted p = 0.018). On the other hand, motor impulsivity subscale score had a significant negative correlation with the FC between the default-mode and salience networks (right supramarginal gyrus, FDR-adjusted p = 0.018; anterior cingulate cortex, FDR-adjusted p = 0.027); this trend was observed in healthy controls. The attentional and non-planning impulsivity, regarded as ‘cognitive’ impulsivity, may be associated with dysfunction in integration of perceptual information and flexible cognitive control in PD.

Measuring impulsivity in Parkinson's disease: a correlational and structural neuroimaging study using different tests

BACKGROUND AND PURPOSE

Impulsivity is an aspect of personality and a major component of multiple neuropsychiatric conditions. In Parkinson's disease, it has been associated with the expression of impulse control disorders, a highly prevalent non-motor complication. Even though multiple tests of impulsivity have been used in this context, the impact of test choice has not been addressed. The aim was to evaluate whether different impulsivity measures in Parkinson's disease share substantial inter-scale and anatomical correlations or rather mirror different underlying phenomena.

METHODS

In a consecutive sample of 89 Parkinson's disease patients without impulse control disorders, four common tests were evaluated assessing different aspects of impulsivity: impulsiveness trait, decisions under implicit risk with and without losses, and delay discounting. Correlations among test scores were analysed and each score was used as a regressor in a set of grey matter volume (GMV) voxel-based morphometry analyses to explore their brain structural correlates.

RESULTS

No significant correlations were found between the different impulsivity tests. Furthermore, their structural brain correlates were divergent. Impulsiveness trait appeared to be associated with lower GMV in dorsal-lateral prefrontal cortices, implicit risk (with losses) with higher GMV in the left nucleus accumbens and lower left insular GMV, implicit risk (without losses) with higher GMV in the left lingual gyrus and lower GMV in the gyri recti and delay discounting with higher GMV in the left nucleus accumbens.

CONCLUSIONS

In Parkinson's disease, different impulsivity measures reflect very dissimilar behavioural and brain structural correlates. Our results suggest that parkinsonian impulsivity is not a unitary phenomenon but rather a heterogeneous entity.

Behavioral and Neuroanatomical Account of Impulsivity in Parkinson's Disease

Impulse control disorder (ICD) is a major non-motor complication of Parkinson's disease (PD) with often devastating consequences for patients' quality of life. In this study, we aimed to characterize the phenotype of impulsivity in PD and its neuroanatomical correlates.

Methods: Thirty-seven PD patients (15 patients with ICD, 22 patients without ICD) and 36 healthy controls underwent a neuropsychological battery. The test battery consisted of anxiety and depression scales, self-report measures of impulsivity (Barratt scale and UPPS-P), behavioral measures of impulsive action (Go/No-Go task, Stop signal task) and impulsive choice (Delay discounting, Iowa gambling task), and measures of cognitive abilities (working memory, attention, executive function). Patients and controls underwent structural MRI scanning.

Results: Patients with ICD had significantly higher levels of self-reported impulsivity (Barratt scale and Lack of perseverance from UPPS-P) in comparison with healthy controls and non-impulsive PD patients, but they performed similarly in behavioral tasks, except for the Iowa gambling task. In this task, patients with ICD made significantly less risky decisions than patients without ICD and healthy controls. Patients without ICD did not differ from healthy controls in self-reported impulsivity or behavioral measurements. Both patient groups were more anxious and depressive than healthy controls. MRI scanning revealed structural differences in cortical areas related to impulse control in both patient groups. Patients without ICD had lower volumes and cortical thickness of bilateral inferior frontal gyrus. Patients with ICD had higher volumes of right caudal anterior cingulate and rostral middle frontal cortex.

Conclusions: Despite the presence of ICD as confirmed by both clinical follow-up and self-reported impulsivity scales and supported by structural differences in various neural nodes related to inhibitory control and reward processing, patients with ICD performed no worse than healthy controls in various behavioral tasks previously hypothesized as robust impulsivity measures. These results call for caution against impetuous interpretation of behavioral tests, since various factors may and will influence the ultimate outcomes, be it the lack of sensitivity in specific, limited ICD subtypes, excessive caution of ICD patients during testing due to previous negative experience rendering simplistic tasks insufficient, or other, as of now unknown aspects, calling for further research.

Validation of the Korean Version of the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease Rating Scale

Background and Purpose

Impulse-control disorder is an important nonmotor symptom of Parkinson's disease (PD) that can lead to financial and social problems, and be related to a poor quality of life. A nationwide multicenter prospective study was performed with the aim of validating the Korean Version of the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease Rating Scale (K-QUIP-RS).

Methods

The K-QUIP-RS was constructed using forward and backward translation, and pretesting of the prefinal version. PD patients on stable medical condition were recruited from 27 movement-disorder clinics. Participants were assessed using the K-QUIP-RS and evaluated for parkinsonian motor and nonmotor statuses and for PD-related quality of life using a predefined evaluation battery. The test–retest reliability of the K-QUIP-RS was assessed over an interval of 10–14 days, and correlations between the KQUIP-RS and other clinical scales were analyzed.

Results

This study enrolled 136 patients. The internal consistency of the K-QUIP-RS was indicated by a Cronbach's α coefficient of 0.846, as was the test–retest reliability by a Guttman split-half coefficient of 0.808. The total K-QUIP-RS score was positively correlated with the scores for depression and motivation items on the Unified PD Rating Scale (UPDRS), Montgomery-Asberg Depression Scale, and Rapid-Eye-Movement Sleep-Behavior-Disorders Questionnaire. The total K-QUIP-RS score was also correlated with the scores on part II of the UPDRS and the PD Quality of Life-39 questionnaire, and the dopaminergic medication dose.

Conclusions

The K-QUIP-RS appears to be a reliable assessment tool for impulse-control and related behavioral disturbances in the Korean PD population.

Risk factors for impulse control disorders and related behaviors in Parkinson's disease: secondary analyses of the ICARUS study

Objective: Impulse control disorders and related behaviors (ICDs) are common in patients with Parkinson’s disease (PD), yet incidence and predictive factors are not fully understood. We examined the epidemiology of ICDs in PD through secondary and post-hoc analyses of data from the ICARUS (SP0990) study, which enrolled >1000 patients.

Methods: Using a modified-Minnesota Impulsive Disorders Interview (mMIDI), ICD incidence was calculated for patients who were ICD-negative at baseline but ICD-positive at year 1, and year 1 and/or 2 (cumulative 2-year ICD incidence). The proportion of “new cases” (ICD-negative at baseline, but ICD-positive at year 1 or 2), and “remitters” (ICD-positive at baseline but ICD-negative at year 1 or 2) was also calculated for the whole ICARUS population.

Results: Among 709 patients ICD-negative at baseline, 97 screened ICD-positive (13.7%) at year 1. Among 712 patients who were ICD-negative at baseline, 147 were ICD-positive at ≥1 post-baseline visit (20.6%). Among patients who were ICD-negative at baseline who subsequently experienced an ICD, a higher proportion were male or smokers, younger at baseline, younger at disease/symptom onset, and had longer disease duration. Among the whole population, a similar proportion were “new cases” at years 1 (9.7%) and 2 (8.6%) versus the previous visit. The proportion of “remitters” was slightly higher at year 2 (11.0%) than 1 (9.1%) versus previous visit.

Conclusions: The proportion of ICD-remitters approximately matched/exceeded new cases, suggesting patients with ICD are in a state of flux. Current data allow for a conservative estimate of 2-year ICD incidence in ICARUS of ∼21% of patients, not accounting for transient new ICD cases between visits.

Impulse control disorders in Parkinson's disease versus in healthy controls: A different predictive model

Impulse control disorders (ICDs), including compulsive gambling, buying, sexual behaviour and eating, are not only a severe disorder that can affect the general, non-clinical population, but also a serious, increasingly recognized psychiatric complication in Parkinson's disease (PD). Previous research detected some risk factors for their occurrence in PD patients and in the general population, including impulsivity. However, impulsivity is a multidimensional construct that comprises several aspects, including reflection impulsivity and delay discounting. The present work assessed different facets of impulsivity in both PD patients and in the healthy controls (HCs) to examine whether they scored differently, and if the occurrence of ICDs in PD patients and in the HCs was predicted by different aspects of impulsivity. The results showed that ICDs in PD patients were predicted by a strong preference for immediate rewards, whereas ICDs in the HCs were predicted by a deficient reflective ability. The present findings may help clinicians in the early identification of PD patients who could develop ICDs by simply assessing their impulsivity in terms of delay discounting. Furthermore, this work contributed to identify another risk factor for ICDs in the non-clinical population.

Impulse control symptoms in patients with Parkinson's disease: The influence of dopaminergic agonist

BACKGROUND

Impulse control disorders and punding are common in Parkinson's disease patients. Cross-sectional studies suggest an association between dopamine replacement therapy, especially dopaminergic agonists, and impulse control and related disorders in Parkinson's disease. However, some surveys suggest that Parkinson's disease itself does not confer an altered risk for impulse control disorders and related behavior, although these disturbances are more frequently reported in Parkinsonian patients than in healthy controls.

OBJECTIVE

To ascertain the frequency of impulse control disorders and punding symptoms in Parkinson's disease patients and healthy controls and to determine the influence of dopamine agonist treatment on the prevalence of these disturbances.

METHODS

A case-control study was conducted on 207 Parkinson's disease patients (79 taking dopamine agonists) and 230 healthy controls. The outcome measures were the presence of current impulse control disorders and punding symptoms, based on clinical criteria after application of the Minnesota Impulsive Disorders Interview for screening.

RESULTS

The frequency of impulse control disorders in Parkinson's disease patients vs. Healthy controls was 16.9% vs. 15.2% (p = 0.631). Punding was more frequent in Parkinson's disease patients (p = 0.028); however, impulse control disorders were more frequent in medicated Parkinson's disease patients taking dopamine agonists than in medicated patients not taking dopamine agonists (p = 0.001) and healthy controls (p = 0.014).

CONCLUSIONS

Parkinson's disease itself does not lead to the development of impulse control disorders. Dopaminergic agonist treatment may trigger the disorder in susceptible individuals. Punding may be more prevalent in Parkinson's disease patients.

Impulse control disorders in Parkinson's disease: A systematic review on the psychometric properties of the existing measures

Background

A significant percentage of patients suffering from Parkinson’s Disease (PD) experience Impulse Control Disorders (ICDs), contributing to reduced quality of life. As they can be managed by reducing the dopamine dosage, the detection of their presence is crucial for PD treatment plan. Nevertheless, they tend to be under-recognized in clinical practice, since routine screening is not common–despite existing instruments that may support clinicians. This work presents a systematic review on the psychometric properties of instruments measuring ICDs in PD, to test whether clinicians dispose of valid tools that may help them in clinical assessment.

Method

A systematic literature search in three databases (EMBASE, MEDLINE, and PsycINFO) was conducted. Quality of the instruments’ psychometric properties was evaluated with Terwee et al.’s criteria, and methodological quality of the studies was evaluated with the COSMIN Checklist.

Results

Ten studies examining seven instruments were selected. The Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease (QUIP) and the Ardouin Scale of Behavior in Parkinson’s Disease (ASBPD) resulted to be the best from a psychometric point of view.

Conclusions

Though the gold standard for diagnosis remains a detailed diagnostic interview, this review will encourage clinicians to use validated tools to accurately assess ICDs.

Rescuing Suboptimal Outcomes of Subthalamic Deep Brain Stimulation in Parkinson Disease by Surgical Lead Revision

BACKGROUND

Clinical trials have established subthalamic deep-brain-stimulation (STN-DBS) as a highly effective treatment for motor symptoms of Parkinson disease (PD), but in clinical practice outcomes are variable. Experienced centers are confronted with an increasing number of patients with partially “failed” STN-DBS, in whom motor benefit doesn’t meet expectations. These patients require a complex multidisciplinary and standardized workup to identify the likely cause.

OBJECTIVE

To describe outcomes in a series of PD patients undergoing lead revision for suboptimal motor benefit after STN-DBS surgery and characterize selection criteria for surgical revision.

METHODS

We investigated 9 PD patients with STN-DBS, who had unsatisfactory outcomes despite intensive neurological management. Surgical revision was considered if the ratio of DBS vs levodopa-induced improvement of UPDRS-III (DBS-rr) was below 75% and the electrodes were found outside the dorsolateral STN.

RESULTS

Fifteen electrodes were replaced via stereotactic revision surgery into the dorsolateral STN without any adverse effects. Median displacement distance was 4.1 mm (range 1.6-8.42 mm). Motor symptoms significantly improved (38.2 ± 6.6 to 15.5 ± 7.9 points, P < .001); DBS-rr increased from 64% to 190%.

CONCLUSION

Patients with persistent OFFmotor symptoms after STN-DBS should be screened for levodopa-responsiveness, which can serve as a benchmark for best achievable motor benefit. Even small horizontal deviations of the lead from the optimal position within the dorsolateral STN can cause stimulation responses, which are markedly inferior to the levodopa response. Patients with an image confirmed lead displacement and preserved levodopa response are candidates for lead revision and can expect significant motor improvement from appropriate lead replacement.

Medications, Deep Brain Stimulation, and Other Factors Influencing Impulse Control Disorders in Parkinson's Disease

Impulse control disorders (ICDs) in Parkinson's disease (PD) have a high cumulative incidence and negatively impact quality of life. ICDs are influenced by a complex interaction of multiple factors. Although it is now well-recognized that dopaminergic treatments and especially dopamine agonists underpin many ICDs, medications alone are not the sole cause. Susceptibility to ICD is increased in the setting of PD. While causality can be challenging to ascertain, a wide range of modifiable and non-modifiable risk factors have been linked to ICDs. Common characteristics of PD patients with ICDs have been consistently identified across many studies; for example, males with an early age of PD onset and dopamine agonist use have a higher risk of ICD. However, not all cases of ICDs in PD can be directly attributable to dopamine, and studies have concluded that additional factors such as genetics, smoking, and/or depression may be more predictive. Beyond dopamine, other ICD associations have been described but remain difficult to explain, including deep brain stimulation surgery, especially in the setting of a reduction in dopaminergic medication use. In this review, we will summarize the demographic, genetic, behavioral, and clinical contributions potentially influencing ICD onset in PD. These associations may inspire future preventative or therapeutic strategies.

Impulsivity across reactive, proactive and cognitive domains in Parkinson's disease on dopaminergic medication: Evidence for multiple domain impairment

Impulse control disorders (ICD) may occur in Parkinson’s disease (PD) although it remains to be understood if such deficits may occur even in the absence of a formal ICD diagnosis. Moreover, studies addressing simultaneously distinct neurobehavioral domains, such as cognitive, proactive and reactive motor impulsivity, are still lacking. Here, we aimed to investigate if reactive, proactive and cognitive impulsivity involving risk taking are concomitantly affected in medicated PD patients, and whether deficits were dependent on response strategies, such as speed accuracy tradeoffs, or the proportion of omission vs. commission errors. We assessed three different impulsivity domains in a sample of 21 PD patients and 13 matched controls. We found impaired impulsivity in both reactive (p = 0.042) and cognitive domains (p = 0.015) for the PD patients, irrespective of response strategy. For the latter, effect sizes were larger for the actions related with reward processing (p = 0.017, d_Cohen = 0.9). In the proactive impulsivity task, PD patients showed significantly increased number of omissions (p = 0.041), a response strategy which was associated with preserved number of commission errors. Moreover, the number of premature and proactive response errors were correlated with disease stage. Our findings suggest that PD ON medication is characterized compared to healthy controls by impairment across several impulsivity domains, which is moderated in the proactive domain by the response strategy.

Behavioural and trait changes in parkinsonian patients with impulse control disorder after switching from dopamine agonist to levodopa therapy: results of REIN-PD trial

OBJECTIVE

In this multicentre open-label trial, we compared behavioural and neuropsychiatric symptoms in Parkinson's disease (PD) patients with impulse control disorders (ICD) treated with dopamine agonists before and 12 weeks after substituting dopamine agonists with an equivalent dose of levodopa/carbidopa slow-release formulation.

METHODS

Baseline characteristics of 50 PD patients with ICD were compared with those of 60 medicated and 40 drug-naive PD control groups. Neuropsychiatric trait changes in the PD-ICD group were investigated 12 weeks after the intervention. ICD behaviours were assessed via modified Minnesota Impulsive Disorders Interview (mMIDI), whereas parkinsonian severity and neuropsychiatric characters were systematically assessed with the Unified PD Rating Scale (UPDRS) and a predefined neuropsychological assessment battery.

RESULTS

At baseline, ICD patients showed higher scores in the Neuropsychiatric Inventory and anxiety, anger and obsessive-compulsive traits compared with both PD control groups. In contrast, the three PD groups showed indifference in the impulsivity scales. At 12 weeks post intervention, ICD behaviours significantly improved (p<0.001, Δ modified MIDI score=‒5.27 ± 5.75) along with the UPDRS II daily activity scores (p=0.02, Δ=‒2.07 ± 4.53). Behavioural disinhibition tended to improve (p=0.06), although no significant changes were observed in the Neuropsychiatric Inventory and personality trait scores. Dopamine agonist withdrawal syndrome developed in 5.3% of the PD-ICD group.

CONCLUSIONS

This study provides class IV evidence suggesting that switching from dopamine agonists to levodopa/carbidopa slow-release formulations alleviated ICD behaviours in PD patients leading to improvement in daily activities whereas neuropsychiatric traits associated with ICD persisted after the 12-week therapy.

TRIAL REGISTRATION NUMBER

NCT01683253.

Impulse Control Disorder in Parkinson's Disease: A Meta-Analysis of Cognitive, Affective, and Motivational Correlates

Background: In Parkinson's disease (PD), impulse control disorders (ICDs) develop as side-effect of dopaminergic replacement therapy (DRT). Cognitive, affective, and motivational correlates of ICD in medicated PD patients are debated. Here, we systematically reviewed and meta-analyzed the evidence for an association between ICD in PD and cognitive, affective, and motivational abnormalities. Methods: A systematic review and meta-analysis was performed on PubMed, Science Direct, ISI Web of Science, Cochrane, EBSCO for studies published between 1-1-2000 and 8-3-2017 comparing cognitive, affective, and motivational measures in PD patients with ICD (ICD+) vs. those without ICD (ICD-). Exclusion criteria were conditions other than PD, substance and/or alcohol abuse, dementia, drug naïve patients, cognition assessed by self-report tools. Standardized mean difference (SMD) was used, and random-effect model applied. Results: 10,200 studies were screened (title, abstract), 79 full-texts were assessed, and 25 were included (ICD+: 625 patients; ICD-: 938). Compared to ICD-, ICD+ showed worse performance reward-related decision-making (0.42 [0.02, 0.82], p = 0.04) and set-shifting tasks (SMD = -0.49 [95% CI -0.78, -0.21], p = 0.0008). ICD in PD was also related to higher self-reported rate of depression (0.35 [0.16, 0.54], p = 0.0004), anxiety (0.43 [0.18, 0.68], p = 0.0007), anhedonia (0.26 [0.01, 0.50], p = 0.04), and impulsivity (0.79 [0.50, 1.09], p < 0.00001). Heterogeneity was low to moderate, except for depression (I² = 61%) and anxiety (I² = 58%). Conclusions: ICD in PD is associated with worse set-shifting and reward-related decision-making, and increased depression, anxiety, anhedonia, and impulsivity. This is an important area for further studies as ICDs have negative impact on the quality of life of patients and their caregivers.

Impulse-Control Disorders in Parkinson's Disease: A Meta-Analysis and Review of Case-Control Studies

BACKGROUND

Although several case-control studies on the prevalence of Impulse-Control Disorders (ICDs) in Parkinson's Disease (PD) have been conducted, no meta-analytic study on this topic has previously been published. Thus, knowledge about the overall prevalence rate of ICD in PD and factors that might moderate this relationship is lacking.

METHOD

Prevalence studies of ICDs in PD were identified by computer searches in the MEDLINE, PsycINFO, and Web of Science databases, covering the period from January 2000 to February 2017. Data for N = 4,539, consisting of 2,371 PD patients and 2,168 healthy controls, representing 14 case-control studies were included. Estimation of the odds ratio (OR) of ICDs in PD compared to healthy controls was conducted using random-effects models. Mixed-effects models were applied in the moderator analysis of heterogeneity. Publication bias was estimated using a contour-enhanced funnel plot, the Rüker's test, and fail-safe N test for estimating the number of potential missing studies.

RESULTS

Overall, the results showed significantly higher ratios for several ICDs in PD compared to healthy controls with the estimated overall ORs ranging between 2.07, 95% CI [1.26, 3.48], for having any ICDs, and 4.26, 95% CI [2.17, 8.36], for hypersexuality. However, the random-effects results for shopping were non-significant, though the fixed-effects model was significant (OR = 1.66, 95%CI [1.21, 2.27]). The testing of potential moderator variables of heterogeneity identified the following two variables that were both associated with increased risk: being medically treated for PD and disease duration. The results must be interpreted with some caution due to possible small-studies effect or publication bias.

CONCLUSION

Individuals with PD seem to have a significantly greater risk of suffering from ICDs compared to healthy controls. Gambling, hypersexuality, eating, punding, and hobbying are all ICDs significantly associated with PDs being medically treated for PD.

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.

Demographic and Clinical Predictors of Trait Impulsivity in Parkinson's Disease Patients

Background

Impulsive behaviour has become increasingly recognised as a neuropsychiatric complication of Parkinson's disease (PD). Thought to be a product of compromised cognitive control, the spectrum of impulsive behaviours in PD ranges from cognitive disinhibition to impulse control disorders (ICDs).

Objective

At present, there are no indicators for trait impulsivity in PD. The objective of the current study was to identify demographic and clinical predictors of susceptibility to trait impulsivity in a cohort of PD patients.

Methods

The current study assessed impulsivity using the Barratt Impulsiveness Scale 11 (BIS-11) in a cohort of 87 PD patients. General linear models (GLMs) were used to identify clinical and demographic variables predictive of heightened BIS-11 second-order attentional and nonplanning subscale scores.

Results

Male gender, no history of smoking, postsecondary education, and heightened disease severity were predictive of increased BIS-11 attentional scores (p < 0.05). Similarly, male gender, after secondary education, and disease severity were predictive of increased BIS-11 nonplanning scores (p < 0.05). Contrary to previous reports, dopaminergic medication use was not a significant determinant of either BIS-11 subscale scores.

Conclusions

Several demographic and clinical variables including male gender, no history of past smoking, after secondary education, and elevated disease severity are associated with impulsivity in PD.

Impulse control disorders in Parkinson's disease

Impulse control disorders (ICD) are frequent side effects of dopamine replacement therapy (DRT) used in Parkinson's disease (PD) with devastating consequences on the patients and caregivers. ICD are behavioural addictions including compulsive gambling, shopping, sexual behaviour, and binge eating that are mainly associated with dopamine D2/D3 agonists. Their management is a real clinical challenge due to the lack of therapeutic alternative. Clinical studies have identified demographic and clinical risk factors for ICD such as younger age at disease onset, male gender, prior history of depression or substance abuse, REM sleep behaviour disorders and higher rate of dyskinesia. PD patients with ICD may also have a specific pattern of dopaminergic denervation in the ventral striatum. Specific evaluation tools have now been designed to better evaluate the severity and impact of ICD in PD. Patients with ICD display altered processing of reward and loss, and decisional bias associated with altered activity in cortical and subcortical areas such as the orbitofrontal cortex, amygdala, insula, anterior cingular cortex, and ventral striatum. Preclinical studies have demonstrated that D2/D3 agonists induce impairments in behavioural processes likely relevant to ICD such as risk-taking behaviour, preference for uncertainty, perseverative responding and sustained drive to engage in gambling-like behaviour. Whether interactions between dopamine denervation and DRT significantly contribute to the pathogenesis of ICD remains poorly understood so far, although features unique to PD have been identified in patients with ICD. Large-scale longitudinal studies are needed to better identify subjects with increased risk to develop ICD and develop therapeutic options.

ICARUS study: prevalence and clinical features of impulse control disorders in Parkinson's disease

BACKGROUND

Impulse control disorders/other compulsive behaviours ('ICD behaviours') occur in Parkinson's disease (PD), but prospective studies are scarce, and prevalence and clinical characteristics of patients are insufficiently defined.

OBJECTIVES

To assess the presence of ICD behaviours over a 2-year period, and evaluate patients' clinical characteristics.

METHODS

A prospective, non-interventional, multicentre study (ICARUS (Impulse Control disorders And the association of neuRopsychiatric symptoms, cognition and qUality of life in ParkinSon disease); SP0990) in treated Italian PD outpatients. Study visits: baseline, year 1, year 2. Surrogate primary variable: presence of ICD behaviours and five ICD subtypes assessed by modified Minnesota Impulsive Disorder Interview (mMIDI).

RESULTS

1069/1095 (97.6%) patients comprised the Full Analysis Set. Point prevalence of ICD behaviours (mMIDI; primary analysis) was stable across visits: 28.6% (306/1069) at baseline, 29.3% (292/995) at year 1, 26.5% (245/925) at year 2. The most prevalent subtype was compulsive eating, followed by punding, compulsive sexual behaviour, gambling and buying disorder. Patients who were ICD positive at baseline were more likely to be male, younger, younger at PD onset, have longer disease duration, more severe non-motor symptoms (including mood and sexual function), depressive symptoms, sleep impairment and poorer PD-related quality of life. However, they did not differ from the ICD-negative patients in their severity of PD functional disability, motor performance and cognitive function.

CONCLUSIONS

Prevalence of ICD behaviours was relatively stable across the 2-year observational period. ICD-positive patients had more severe depression, poorer sleep quality and reduced quality of life.

A Comparison of Treatment-Seeking Behavioral Addiction Patients with and without Parkinson's Disease

The administration of dopaminergic medication to treat the symptoms of Parkinson's disease (PD) is associated with addictive behaviors and impulse control disorders. Little is known, however, on how PD patients differ from other patients seeking treatments for behavioral addictions. The aim of this study was to compare the characteristics of behavioral addiction patients with and without PD. N = 2,460 treatment-seeking men diagnosed with a behavioral addiction were recruited from a university hospital. Sociodemographic, impulsivity [Barratt Impulsiveness Scale (BIS-11)], and personality [Temperament and Character Inventory-Revised (TCI-R)] measures were taken upon admission to outpatient treatment. Patients in the PD group were older and had a higher prevalence of mood disorders than patients without PD. In terms of personality characteristics and impulsivity traits, PD patients appeared to present a more functional profile than PD-free patients with a behavioral addiction. Our results suggest that PD patients with a behavioral addiction could be more difficult to detect than their PD-free counterparts in behavioral addiction clinical setting due to their reduced levels of impulsivity and more standard personality traits. As a whole, this suggests that PD patients with a behavioral addiction may have different needs from PD-free behavioral addiction patients and that they could potentially benefit from targeted interventions.

Impulsive oculomotor action selection in Parkinson's disease

The effects of Parkinson's disease (PD) on the dynamics of impulsive action selection and suppression have recently been studied using distributional analyses, but with mixed results, especially for selection. Furthermore, some authors have suggested that impulsivity, regarded as a personality trait, shares common features with behavioral tasks' measures. The current study was designed to clarify the impact of PD on impulsive action selection and suppression, and investigate the link between cognitive action control and self-reported impulsivity. We administered an oculomotor version of the Simon task to 32 patients with PD and 32 matched healthy controls (HC), and conducted distributional analyses in accordance with the activation-suppression model. Patients and HC also filled out the Barratt Impulsiveness Scale (BIS) questionnaire. Results showed that patients with PD were faster overall and exhibited a greater congruence effect than HC. They also displayed enhanced impulsive action selection. By contrast, the suppression of impulsive responses was similar across both groups. Furthermore, patients had higher impulsivity scores, which were correlated with higher impulsive action selection and higher suppression. Our study yielded two interesting findings. First, PD resulted in a higher number of fast errors. The activation-suppression model suggests that patients with PD are more susceptible to the impulsive action selection induced by the irrelevant stimulus dimension. Second, impulsive action selection and suppression were both associated with trait impulsivity, as measured by the BIS, indicating that these two aspects of impulsivity share common features.

A multidimensional approach to impulsivity in Parkinson's disease: measurement and structural invariance of the UPPS Impulsive Behaviour Scale

BACKGROUND

Poor impulse control is a common feature in patients with Parkinson's disease (PD). However, before testing whether patients with PD and controls differ in impulsivity, one must assess whether impulsivity measures are invariant across groups. Consequently, we examined (a) the measurement and structural invariance of a scale assessing changes in four dimensions of impulsivity (urgency, lack of premeditation, lack of perseverance and sensation seeking) among patients with PD and controls; and (b) whether the four impulsivity traits relate differentially to risky decisions by patients.

METHOD

Close relatives of 78 patients with idiopathic PD and 96 control participants were given the short Urgency-Premeditation-Perseverance-Sensation seeking Impulsive Behaviour Scale (UPPS), which assesses changes in four dimensions of impulsivity. Participants also completed the Game of Dice Task (GDT), a laboratory measure of risk taking.

RESULTS

Multigroup confirmatory factor analyses supported measurement invariance across groups, whereas structural invariance was not confirmed. Patients with PD showed greater variability and higher impulsivity than controls. Furthermore, patients with impulse control disorders (ICDs) demonstrated even greater levels of sensation seeking than patients without ICDs. Finally, lower premeditation and greater perseverance were significantly associated with greater risk taking in patients with PD, and higher agonist dopaminergic doses with less risky choices on the GDT.

CONCLUSIONS

The questionnaire appears to function comparably across patients and controls. Thus, group comparisons on the questionnaire can be considered valid. Mean differences between groups on the dimensions of impulsivity may reflect executive impairments and/or abnormal reward processing in patients with PD, which may lead to risky behaviours.

Introduction to Parkinson disease (PD) and its complications

Parkinson disease (PD) is a common neurodegenerative disorder in older adults characterized by motor and nonmotor symptoms and complications. Impulse control disorders (ICDs), such as pathological gambling, compulsive shopping, compulsive sexual behavior (hypersexuality), and binge eating disorder, affect 13.6% of the PD population. Use of dopamine receptor agonists (DRAs) is considered a major risk factor for ICD development. Amantadine and a high dose of levodopa were linked to ICDs to a lesser extent than DRAs. Based on the severity of behavior(s), ICDs can negatively impact social, professional, and familial lives of patients and their families. Ideally, all PD patients taking DRAs, high doses of levodopa, and/or amantadine should be routinely asked about or monitored for ICDs during therapy initiation and continuation. Dose decrease or withdrawal of the offending agent, primarily DRAs, is usually the most effective first step in ICD management. Careful dose adjustment with close monitoring is warranted due to risk for worsening of motor symptoms or emergence of dopamine agonist withdrawal syndrome (DAWS). About 1/3 of PD patients with ICD who decrease or discontinue DRA experienced DAWS. The lowest dose of DRA will need to be continued to balance ICDs and DAWS as it is not alleviated by other dopaminergic or psychotropic medications. Other therapies with low empiric evidence, such as amantadine, naloxone, cognitive behavior therapy, deep brain stimulation, and psychopharmacotherapy showed mixed results for ICD management. It is crucial that clinicians are familiar with the psychiatric complications of PD, including ICDs, beyond mere recognition and management of motor symptoms.

Impulse control disorders in Parkinson's disease: Predominant role of psychological determinants

OBJECTIVES

Impulse Control Disorders (ICDs) in Parkinson's disease (PD) have previously almost exclusively been considered to result from anti-parkinsonian medication. However, this biomedical perspective has failed to achieve a full understanding of the phenomenon and it is argued that a failure to consider psychological factors is a critical omission.

DESIGN

The present study examined the predictive relationship between ICDs in PD and a range of psychological measures, whilst controlling for a number of biomedical determinants.

MAIN OUTCOME MEASURES

One hundred participants with idiopathic PD completed questionnaires that assessed demographic and clinical characteristics, psychological measures and the presence of ICDs (QUIP-RS).

RESULTS

Increased use of a 'negative' coping strategy, stronger illness identity, more emotional illness representations and stress were found to be significant predictors of ICDs, and different psychological predictors were associated with different ICDs. Medication was not found to predict ICDs in the presence of psychological factors, either when total treatment levels were considered or when agonist dose was considered alone.

CONCLUSIONS

This study provides the first quantitative evidence of a predominant predictive relationship between psychological factors and ICDs in PD. The results suggest that psychological interventions may have useful therapeutic role to play for ICDs in PD.

Impact of Sex on the Nonmotor Symptoms and the Health-Related Quality of Life in Parkinson's Disease

Background. Female Parkinson's disease (PD) patients seem to experience not only more severe motor complications and postural instability but also more pronounced depression, anxiety, pain, and sleep disturbances. Objective. The aim of the present study was to evaluate the role of sex as a possible independent predictor of HRQoL in PD. Methods. In this cross-sectional study, 621 consecutive patients treated at the University of Pécs were enrolled. Severity of PD symptoms was assessed by MDS-UPDRS, UDysRS, Non-Motor Symptoms Scale, PDSS-2, Hamilton Anxiety Scale, Montgomery-Asberg Depression Rating Scale, Lille Apathy Rating Scale, and Addenbrooke Cognitive Examination. HRQoL was assessed by PDQ-39 and EQ-5D. Multiple regression analysis was performed to estimate the PDQ-39 and EQ-5D index values based on various clinical factors. Results. Although females received significantly lower dosage of levodopa, they had significantly more disabling dyskinesia and worse postural instability. Anxiety, pain, sleep disturbances, and orthostatic symptoms were more frequent among females while sexual dysfunction, apathy, and daytime sleepiness were more severe among males. Women had worse HRQoL than men (EQ-5D index value: 0.620 ± 0.240 versus 0.663 ± 0.229, p = 0.025, and PDQ-39 SI: 27.1 ± 17.0 versus 23.5 ± 15.9, p = 0.010). Based on multiple regression analysis, sex was an independent predictor for HRQoL in PD. Conclusions. Based on our results, female sex is an independent predictor for having worse HRQoL in PD.

How close are we to individualized medicine for Parkinson's disease?

INTRODUCTION

There is a considerable inter-individual heterogeneity in clinical features, disease course, and treatment response in Parkinson's disease (PD), which can be explained not only by disease process and clinical variables, but also by an impact from genetic factors. Evidence-based medicine relies on large randomized control trials and meta-analysis-average medicine, which ignores individual differences. However, we are now in the early phases of a paradigm shift in medicine relating to individuality and variability. The purpose of individualized medicine is to predict patients' responses to targeted therapy using diagnostic tests based on genetics or other molecular mechanisms, thus providing the right drug at the right dose at the right time.

AREAS COVERED

In this article, we outline current state of individualized medicine for PD. Expert Commentary: Pharmacogenomics, an important element of individualized medicine, is just beginning to be considered in PD. To advance the clinical use of pharmacogenomics, big data cohort for genomic research and multidisciplinary team approaches are necessary.

Association between REM sleep behaviour disorder and impulse control disorder in patients with Parkinson's disease

INTRODUCTION

The relationship between impulse control disorder (ICD) and REM sleep behaviour disorder (RBD) has not yet been clarified, and the literature reports contradictory results. Our purpose is to analyse the association between these 2 disorders and their presence in patients under dopaminergic treatment.

METHODS

A total of 73 patients diagnosed with Parkinson's disease and treated with a single dopamine agonist were included in the study after undergoing clinical assessment and completing the single-question screen for REM sleep behaviour disorder and the short version of the questionnaire for impulsive-compulsive behaviours in Parkinson's disease.

RESULTS

Mean age was 68.88 ± 7.758 years. Twenty-six patients (35.6%) were classified as probable-RBD. This group showed a significant association with ICD (P=.001) and had a higher prevalence of non-tremor akinetic rigid syndrome and longer duration of treatment with levodopa and dopamine agonists than the group without probable-RBD. We found a significant correlation between the use of oral dopamine agonists and ICD. Likewise, patients treated with oral dopamine agonists demonstrated a greater tendency toward presenting probable-RBD than patients taking dopamine agonists by other routes; the difference was non-significant.

CONCLUSIONS

The present study confirms the association between RBD and a higher risk of developing symptoms of ICD in Parkinson's disease.

Psychiatric Conditions in Parkinson Disease: A Comparison With Classical Psychiatric Disorders

Psychiatric conditions often complicate the outcome of patients affected by Parkinson disease (PD), but they differ from classical psychiatric disorders in terms of underlying biological mechanisms, clinical presentation, and treatment response. The purpose of the present review is to illustrate the biological and clinical aspects of psychiatric conditions associated with PD, with particular reference to the differences with respect to classical psychiatric disorders. A careful search of articles on main databases was performed in order to obtain a comprehensive review about the main psychiatric conditions associated with PD. A manual selection of the articles was then performed in order to consider only those articles that concerned with the topic of the review. Psychiatric conditions in patients with PD present substantial differences with respect to classical psychiatric disorders. Their clinical presentation does not align with the symptom profiles represented by Diagnostic and Statistical Manual for Mental Disorders and International Classification of Diseases. Furthermore, psychiatry treatment guidelines are of poor help in managing psychiatric symptoms of patients with PD. Specific diagnostic tools and treatment guidelines are needed to allow early diagnosis and adequate treatment of psychiatric conditions in comorbidity with PD.

Does response inhibition have pre- and postdiagnostic utility in Parkinson's disease?

Parkinson's disease (Pd) is the second most prevalent degenerative neurological condition worldwide. Improving and sustaining quality of life is an important goal for Parkinson's patients. Key areas of focus to achieve this goal include earlier diagnosis and individualized treatment. In this review the authors discuss impulse control in Pd and examine how measures of impulse control from a response inhibition task may provide clinically useful information (a) within an objective test battery to aid earlier diagnosis of Pd and (b) in postdiagnostic Pd, to better identify individuals at risk of developing impulse control disorders with dopaminergic medication.

Trait Impulsivity and Anhedonia: Two Gateways for the Development of Impulse Control Disorders in Parkinson's Disease?

Apathy and impulsivity are two major comorbid syndromes of Parkinson's disease (PD) that may represent two extremes of a behavioral spectrum modulated by dopamine-dependent processes. PD is characterized by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta to which are attributed the cardinal motor symptoms of the disorder. Dopamine replacement therapy (DRT), used widely to treat these motor symptoms, is often associated with deficits in hedonic processing and motivation, including apathy and depression, as well as impulse control disorders (ICDs). ICDs comprise pathological gambling, hypersexuality, compulsive shopping, binge eating, compulsive overuse of dopaminergic medication, and punding. More frequently observed in males with early onset PD, ICDs are associated not only with comorbid affective symptoms, such as depression and anxiety, but also with behavioral traits, such as novelty seeking and impulsivity, as well as with personal or familial history of alcohol use. This constellation of associated risk factors highlights the importance of inter-individual differences in the vulnerability to develop comorbid psychiatric disorders in PD patients. Additionally, withdrawal from DRT in patients with ICDs frequently unmasks a severe apathetic state, suggesting that apathy and ICDs may be caused by overlapping neurobiological mechanisms within the cortico-striato-thalamo-cortical networks. We suggest that altered hedonic and impulse control processes represent distinct prodromal substrates for the development of these psychiatric symptoms, the etiopathogenic mechanisms of which remain unknown. Specifically, we argue that deficits in hedonic and motivational states and impulse control are mediated by overlapping, yet dissociable, neural mechanisms that differentially interact with DRT to promote the emergence of ICDs in vulnerable individuals. Thus, we provide a novel heuristic framework for basic and clinical research to better define and treat comorbid ICDs in PD.