METHODS
Participants
     Forty-five patients diagnosed with PD and 45 healthy participants matched on age (in years), gender and education (in years) took part in the study. Patients were recruited from the Outpatients Clinic of the Neurology Department of Papageorgiou and AXEPA Hospitals in Thessaloniki, Greece and the Parkinson Care Association ‘EPICOUROS’ in Athens, Greece. Healthy control participants were recruited from Senior Day Care centers in Thessaloniki and from a research volunteers’ data base from previous studies.
     The inclusion criteria for the patients were: i) diagnosis by a neurologist according to the UK Parkinson’s Disease Society Brain Bank Clinical Diagnostic Criteria (Hughes, Daniel, Kilford, & Lees, 1992), ii) to be at the mild or medium stage of the disease according to the Unified Parkinson’s Disease Rating Scale, iii) a score on the Mini-Mental State Examination (MMSE; Folstein, Folstein, & McHugh, 1975) equal to or above 24 (Fountoulakis, Tsolaki, Chantzi, & Kazis, 2000) iv) no evidence of other types of neurological or psychiatric diseases (except for depression), such as atypical parkinsonism, idiopathic tremor, parkinsonism syndromes or vascular parkinsonism; and v) no evidence of a history of alcohol and other drugs abuse. The inclusion criteria for the control group were: i) a score on the MMSE equal to or above 24; ii) no history of neurological or psychiatric disease; iii) no evidence of a history of alcohol and other drugs abuse.
     The study was approved by the University of Sheffield Ethics Committee, and informed written consent was obtained from all the participants. Parkinson’s disease patients had a time since diagnosis of typically over nine years, and disability scale scores that were consistent with the earlier stages of the condition, with a reasonable level of independence. Almost all patients (42) were under medication (levodopa preparations and/or dopamine receptor agonists) at the time of the study. The levodopa equivalent daily dose (LEDD) was calculated using the formula proposed by Bliwise, Trotti, Wilson, Greer, Wood?Siverio, Juncos et al. (2012). That is, LEDD = [regular levodopa dose + levodopa continuous-release dose * 0.75 + (regular levodopa dose + (continuous-release levodopa dose * 0.75)) * 0.25 (if taking entacapone)] + [dopamine agonists * 100]). MAO-B inhibitors were assessed as pergolide (1 pill = 100 LEDD).
Measurements and Procedure
Clinical measures
      Unified Parkinson’s Disease Rating Scale (UPDRS). The UPDRS (Fahn, Elton, and Members of the UPDRS development committee, 1987) is used to confirm a diagnosis of PD, evaluate the severity of the disease and establish specific impairments. In the present study, a new version (MDS-UPDRS) developed by the Movement Disorder Society (MDS; Goetz, Fahn, Martinez?Martin, Poewe, Sampaio, Stebbins et al., 2007) was employed. The MDS-UPDRS consists of 65 items, 48 of them are rated with 0 (none) to 4 (severe), whereas 7 items require a yes/no response. Only Part III was employed, where patients’ impairment is described in percentage terms, ranging from 0% (maintaining only vegetative functions) to100% (being completely independent).
      Hoehn &Yahrscale (Hoehn &Yahr, 1967). The Hoehn & Yahrscale was developed to evaluate symptom severity for PD and its use is supported by the Movement Disorder Society Task Force for Rating Scales for Parkinson's disease (Goetz et al., 2004). The scale rates the stage of disease progression, ranging from 0 (no signs of disease) to 5 (wheelchair/bed bound). 
      Both clinical scales were completed by a clinician.
	Hospital Anxiety and Depression Scale (HADS; Zigmond & Snaith, 1983) is a widely used measure of depressive and anxious symptomatology in clinical populations with somatic problems, and it can also be administered to the general population (Bjelland, Dahl, Haug, & Neckelmann, 2002; Mykletun, Stordal, & Dahl, 2001). The HADS includes 14 items, with a scale ranging from 0 (not at all) to 3 (most of the time). The maximum score in the anxiety and depression sub-scales is 21. The HADS has been adapted and validated for the Greek population and has good internal consistency (?= 0.884 for the total scores, and ?=0.829 and 0.840, for the anxiety and depression sub-scales, HADS-A and HADS-D, respectively; Michopoulos, Douzenis, Kalkavoura, Christodoulou, Michalopoulou, Kalemi, et al., 2008).
Impulsivity measures
      The Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s - Disease Rating Scale, (QUIP-RS; Weintraub, Mamikonyan, Papay, Shea, Xie, & Siderowf, 2012) consists of 4 questions, for example ‘How much do you think about the following behaviors….’in relation to gambling, buying, eating and sexual behavior, and 3 related disorders (medication use, pounding, and hobbyism). It uses a 5-point scale, from 0 to 4, to measure frequency of compulsive thoughts and impulsive behaviours in connection with the targeted category. The total combined score for QUIP-RS ranges from 0 to 112. The scale was translated and back-translated by two bilingual Greek-English neuropsychologists for the purpose of this study.
      Barratt Impulsiveness Scale (BIS-11; Patton, Stanford, & Barratt, 1995) was employed to measure behavioral and trait of impulsiveness. The tool consists of 30 items, and the participant is required to answer each item on a 4-point scale from 1(Rarely/Never) to 4 (Almost Always/Always). The scale consists of 3 subscales; Motor Impulsiveness (for example “I buy things on impulse”), Attentional Impulsiveness (for example “I am restless at the theater or lectures”) and Non-planning Impulsiveness (for example “I plan tasks carefully”). The scale has shown good internal consistency (?=.83) (Stanford, Mathias, Dougherty, Lake, Anderson, & Patton, 2009). The BIS-11 has been translated and used in the Greek population (Giotakos, Markianos, Vaidakis, & Christodoulou, 2003).
Self-conscious emotion measures
      The Self-Conscious Affect questionnaire (TOSCA; Tangney, Dearing, Wagner, & Gramzow, 2000) was employed to measure shame and guilt. The scale consists of 16 scenarios (11 negative and 5 positive, for example “You break something at work and then hide it”), and participants self-report their potential reactions using a 5-point scale. TOSCA-3 includes six subscales, shame-proneness, guilt-proneness, externalization, detachment/unconcern, A-pride and B-pride. In this study we analyses only the shame and guilt subscales. The tool has been adapted and validated to the Greek population, and has shown adequate internal consistency (?=.78 for shame-proneness, and ?=.75 for guilt-proneness; Gouva, Kaltsouda, & Paschou, 2012).
      The Self-Disgust Scale (SDS) was developed by Overton et al. (2008) to measure disgust directed towards the Self. This scale has not been used before in the Greek population, so we developed a Greek version of the scale (SDS-Greek, or SDS-G) and conducted a validation study (see below).
Emotion induction experiments
      To our knowledge, there are no previous studies concerning the experimental induction of self-disgust, since self-disgust is a relatively new construct. Thus, we designed two experiments to induce disgust (and other emotions) toward the self.
    Narration-induction experiment. This experiment was based on the paradigm to induce self-conscious emotions developed by Dickerson, Kemeny, Aziz, Kim, and Fahey (2004), in which participants were asked to write down an experience that made them feel a certain way. After obtaining informed consent, participants sat comfortably in a chair, and were instructed to narrate orally instead of writing (on the assumption that the PD patients would find oral narration less taxing) experiences that made them feel ashamed, guilty or self-disgusted. Also they were asked to narrate a neutral experience, something they did the day before. There was no time limit and narrations were recorded using Audacity software.
     The guidelines for the narrations’ induction paradigm were similar to those of Dickerson et al. (2004). However, in the study of Dickerson et al. (2004) participants were asked to write about one traumatic and upsetting experience that made the individual feel bad about him/her -self or blame his/her self, whereas in our study participants narrated three separate traumatic and upsetting experiences in which they felt self-disgust, shame and guilt. Specifically, the instructions for self-disgust were as follow ‘I want you to narrate one of the most traumatic and upsetting experiences of your life; please focus on an experience that you felt disgust towards the self. It could be an experience which made you feel negatively about yourself or a past experience when you did not like yourself. The important thing is that you tell about your deepest thoughts and feelings. Ideally, whatever you speak about should deal with an event or experience that you have not talked with others about in detail’. The same instructions were given for guilt and shame but changing the wording so that participants were encouraged to narrate an incident which made them feel guilty and ashamed, respectively. The instructions for the neutral condition were again similar to those employed in Dickerson et al.’s (2004), ‘I want you to tell about what you did during the past 24 hours. You should describe your activities and schedule in detail, discussing the facts and circumstances as objectively as possible. You might describe what you had for dinner last night, what time you got up this morning, and so forth. The important thing is you discuss the facts and try to remain objective about your activities’.
     After each narration, participants were asked to self-report how they felt using a Visual Analogue Scale (VAS) from 0 (Not at all) to 100 (Extremely). Specifically, they were asked to self-rate the target emotion in the narration (self-disgust, shame or guilt), other non-target emotions (anger, sadness and happiness), and level of arousal (from 0 -I feel completely calm- to 100 -I feel completely excited-).
     Photo-induction of self-disgust. Participants were presented either with a full body picture of themselves or with a neutral picture. On arrival at the experimental setting, and after obtaining informed consent, the participants were asked to sit and pose with a neutral posture while the researcher took a photograph. The neutral photo was selected from the International Affective Picture System (2005), had neutral scores in pleasantness and arousal, and depicted hanging clothes (n.7217). Each photo was presented for 3 s, and the order of the photos was counterbalanced across participants. Participants were asked to view the photos passively, and were instructed as follows, “You will be presented with two consecutive photos. Please look at each photo carefully. After each photo you will be asked to rate how you feel”. 
     After each photo, participants were asked to self-report the target emotion (self-disgust), other non-target emotions (anger and sadness), and arousal levels using Visual Analogue Scales (VASs). 
Procedure
     Data collection lasted three hours approximately, and took place into two sessions. The first session included demographic data and the medical history of the participant, and all the self-report measures. The second session consisted of the emotion induction experiments. Testing took place in a quiet room in the health centers, the Senior Day Care centers, or at the University of Sheffield International Faculty. The picture-induction and the narration-induction procedures took place in a counterbalanced order across participants, and with a break in between.