Correlations of plasma oxytocin with clinical and hormonal parameters in panic disorder.

AIMS: The potential association between oxytocin (OXT) plasma levels and clinical and hormonal parameters in panic disorder (PD) especially in its acute phase - has not been investigated as yet. This was the aim of this article. METHOD: Twenty-four consecutively-referred, acutely-ill, medication-free PD patients with (PDA, N = 21) or without agoraphobia, moreover without comorbidities, completed the following clinical measures: Hamilton Anxiety Rating Scale (HARS); Agoraphobic Cognitions Questionnaire (ACQ); Mobility Inventory-Alone subscale (MI-alone); and number of panic attacks during last 21 d (PA21d). Plasma levels of OXT, adrenocorticotropic hormone (ACTH) and cortisol were evaluated. RESULTS: OXT levels were significantly, negatively associated with the HARS scores (r= -0.59 p=.002) and weakly, negatively correlated with the ACQ scores (r = -0.403 p=.051). No significant correlations were traced between OXT levels and PA21d, MI-alone, ACTH, and cortisol. CONCLUSION: In acutely-ill, medication-free PD patients, OXT plasma levels may be relevant to the severity of their 'general' anxiety symptoms, but not to the 'specific' panic psychopathology.

Pituitary-adrenal axis hormones in early-onset versus late-onset panic disorder.

OBJECTIVE: It has been hypothesised that early-onset panic disorder (PD) may constitute a biologically distinct subtype of PD, but the few relevant data are inconclusive. We systematically explored for potential psychopathological and hormonal differences between early-onset (age at onset ≤ 27 years) versus late-onset PD, in consecutively-referred, medication-free, acutely-ill PD outpatients, moreover without comorbid mental disorders except agoraphobia (N = 54; age = 32.3 ± 7.5 years; early-onset = 27; females = 38). METHODS: Hormones assessed (plasma levels) included adrenocorticotropic hormone (ACTH), cortisol and dehydroepiandrosterone sulphate (DHEAS). Psychopathological measures included panic attacks' number during last three weeks, the Agoraphobic Cognitions and the Body Sensations Questionnaires and the Hamilton Anxiety Rating Scale. RESULTS: Early-onset PD patients - compared to their late-onset counterparts - had longer duration of the disease. The two onset-groups demonstrated similar panic and anxiety symptoms and similar ratios of smokers/never-smokers. However, early-onset patients demonstrated significantly greater ACTH and DHEAS levels and higher (marginally significant) cortisol levels than the late-onset patients. Moreover, in the early-onset patients only, significant positive correlations emerged between ACTH levels and the severity of both panic and anxiety symptomatology. CONCLUSIONS: These findings suggest that the two onset-groups demonstrate significant differences in the hypothalamic-pituitary-adrenal axis functioning, at least when acutely-ill.Key pointsEarly-onset panic disorder (EOPD) may differ biologically from late-onset PD (LOPD).EOPD was correlated with greater adrenocorticotropic hormone (ACTH) plasma levels.EOPD was correlated with greater dehydroepiandrosterone sulphate plasma levels.In EOPD only, ACTH levels were positively correlated with panic and anxiety symptoms.

Stress Hormones as Predictors of Response to Cognitive Behavior Therapy in Panic Disorder.

OBJECTIVE: Data regarding the potential association between the outcome of psychotherapy of panic disorder (PD) and biological parameters are few. In 21 (16 females) consecutively referred, medication-free, acutely ill PD outpatients, without comorbidities, except agoraphobia, we systematically explored for potential neuroendocrine and clinical correlates of response to a brief cognitive behavior therapy (CBT). METHODS: Cortisol and adrenocorticotropic hormone (ACTH) basal plasma levels were measured. Measures of psychopathology: (a) Symptom Checklist-90-Revised (SCL-90-R), (b) Clinical Global Impressions-Improvement (CGI-I) Scale, (c) Agoraphobic Cognitions Questionnaire (ACQ), and (d) Mobility Inventory (MI)-alone subscale. RESULTS: Nonresponders to CBT (CGI-I >2; N = 6) - as compared to the responders (CGI-I ≤2; N = 15) - demonstrated significantly higher cortisol and ACTH basal plasma concentrations. These differences were much stronger when only female patients (nonresponders = 4; responders = 12) were taken into consideration. Regarding psychopathology, nonresponders to CBT suffered from more severe agoraphobia (MI-alone) at baseline. On the contrary, more intense manifestations of anger (SCL-90-R) at baseline were associated with a better treatment outcome. Response to CBT was associated with significant reductions in all SCL-90-R subscales, more pronounced for "phobic anxiety" and "anxiety" subscales. CONCLUSIONS: This study suggests that in acutely ill, medication-free PD patients, response to CBT may be associated with certain hormonal and clinical parameters at baseline.

Validation of the Greek Version of Hedonic, Eudaimonic, and Extrinsic Motives for Activities (HEEMA) Instrument.

Hedonia and eudaimonia are motivating forces through which individuals pursue well-being. The latter is a multidimensional concept, while hedonia and eudaimonia, both of which are realized through the reward system of the brain, are known to influence each other. Researchers have shown that specific extrinsic values (e.g., material wealth, power over other people, etc.) are associated with a sense of "good life" and may influence both hedonia and eudaimonia. The HEEMA (Hedonic, Eudaimonic, and Extrinsic Motives for Activities) scale was developed to evaluate all three ways of seeking well-being, hedonia, eudaimonia, and extrinsic values, in both a healthy and unhealthy fashion. The purpose of this study was to assess the psychometric properties of the HEEMA scale in a sample of 225 Greek individuals. Participants filled the HEEMA, SWLS, MLQ, Self-Esteem questionnaire, DASS-21, MHC-SF, and Big Five Inventory, anonymously. Reliability and validity indices of the scales were satisfactory (Cronbach's α were 0.734, 0.811, and 0.843 for the hedonic, eudaimonic, and extrinsic motives subscales, respectively). Indicatively, the study showed a positive correlation between aspects of well-being and positive emotions, satisfaction with life, sense of meaning and purpose, as well as with specific personality traits, while negative correlations were found between eudaimonic orientation and depression.

Lifetime co-occurring psychiatric disorders in newly diagnosed adults with attention deficit hyperactivity disorder (ADHD) or/and autism spectrum disorder (ASD).

BACKGROUND: Co-occurring psychiatric disorders in adults with Attention Deficit Hyperactivity Disorder (ADHD) and/or Autism Spectrum Disorder (ASD) contribute to the burden of the healthcare and possibly to the delay of diagnosis. Aim of the study was to clinically assess the prevalence and compare lifetime co-occurring psychopathology in a sample of newly diagnosed ADHD and/or ASD adults and discuss the diagnostic challenges they pose. METHODS: The lifetime prevalence rates of ten of the most frequently co-occurring psychiatric diagnoses was registered in 336 adults of normal intelligence who underwent a thorough clinical evaluation for the diagnosis of ADHD and/or ASD for the first time in their lives. Four study groups were formed: the ADHD (n = 151), the ASD (n = 58), the ADHD+ASD (n = 28) and the nonADHD/nonASD (NN) (n = 88) group. RESULTS: At least one co-occurring psychopathology was found in 72.8% of the ADHD group, in 50% of the ASD group, in 72.4% of the ADHD+ASD group and in 76.1% of the NN group (p = 0.004). In all groups the most frequent psychiatric disorder was depressive disorder. The only significant difference regarding the patterns of psychiatric co-occurrence between the ADHD and the nonADHD groups (ASD and NN groups) was found for SUD (p = 0.001). Also, the proportion of subjects with Bipolar Disorder was significantly greater in the NN group as compared to those with ASD (p = 0.025). CONCLUSIONS: Our results support the high prevalence of co-occurring psychiatric disorders in adults with ADHD and/or ASD with the ASD group presenting the lowest rate. The most marked difference between the ADHD and the nonADHD groups was found for SUD. Moreover, our findings highlight the need for a thorough clinical assessment of all referred patients both in the presence and absence of ADHD and/or ASD.

Well-being in Patients with Affective Disorders Compared to Nonclinical Participants: A Multi-Model Evaluation of the Mental Health Continuum-Short Form.

OBJECTIVES: The Mental Health Continuum-Short Form (MHC-SF), measuring emotional, social, and psychological well-being, has scarcely been validated in clinical populations. We evaluated MHC-SF in 203 patients with affective disorders and 163 nonclinical participants. METHOD: Traditional confirmatory factor analysis (CFA), bifactor CFA, three-factor exploratory structural equation modeling (ESEM), and bifactor ESEM models were compared. Convergent/discriminant validity was tested against classic well-being validators and current mood state. RESULTS: All three subscales were significantly lower in patients. Test-retest reliability in patients was moderate. Bifactor ESEM fitted data best and displayed full scalar gender and partial scalar invariance across groups. Factor strength indices suggested that MHC-SF is primarily unidimensional, especially in patients. However, subscales differed considerably on size, internal consistency, distinctness, discriminant validity, and temporal stability. CONCLUSIONS: MHC-SF was valid and reliable for monitoring well-being in both clinical and nonclinical samples, but further research is needed before safely concluding on its dimensionality.

Association of Schizoid and Schizotypal Personality disorder with violent crimes and homicides in Greek prisons.

BACKGROUND: Personality disorders (PDs) have been associated with both violent crimes and homicides in many studies. The proportion of PDs among prisoners reaches up to 80%. For male prisoners, the most common PD in the literature is antisocial PD. The aim of this study was to investigate the association between PDs and violent crimes/homicides of male prisoners in Greece. METHODS: A sample of 308 subjects was randomly selected from a population of 1300 male prisoners incarcerated in two Greek prisons, one urban and one rural. The presence of PDs was assessed using the Mini International Neuropsychiatric Interview (MINI) and the Personality Diagnostic Questionnaire-4 (PDQ-4). Using logistic regression models PD types and PD "Clusters" (independent variables) were associated with "violent/non-violent crimes" and "homicides/non homicides" (dependent variables). RESULTS: "Cluster A" PDs (Paranoid, Schizoid, and Schizotypal) were diagnosed in 16.2%, "Cluster B" (Antisocial, Borderline, Histrionic, Narcissistic) in 66.9% and "Cluster C" (Obsessive-Compulsive, Dependent, Avoidant) in 2.9% of the studied population. Violent crimes and homicides were found significantly associated with "Cluster A" PDs (p = 0.022, p = 0.020). The odds ratio of committing violent crimes was 2.86 times higher for patients with "Cluster A" PDs than the ones without PDs. In addition, the odds ratio of committing homicides was 4.25 times higher for patients with "Cluster A" PDs. In separate analyses, the commitment of violent crimes as well as homicides, was significantly associated with Schizoid (p = 0.043, p = 0.020) and Schizotypal PD (p = 0.017, p = 0.030). CONCLUSIONS: The majority of prisoners was found to suffer from a PD, mainly the Antisocial "Cluster B", but the commitment of violent crimes and homicides was significantly associated only with "Cluster A" PDs and specifically with Schizoid and Schizotypal PD.

Antipsychotic Treatment of 22q11.2 Deletion Syndrome-Related Psychoses.

In the recent study by Verhoeven and Egger, 2015 and the recent letter to the editor by Boot et al. 2015 an emphasis is given to the best possible pharmacological treatment of 22q11-2 Deletion-Syndrome related psychoses. We would like to present the case of a 23-year old Cypriot patient with 22q11.2 deletion syndrome who fulfilled criteria for treatment resistant schizophrenia (TRS). He was sequentially treated with aripiprazole, risperidone, olanzapine, haloperidol and a combination treatment with olanzapine and haloperidol. Clozapine was the only antipsychotic medication that has improved his condition.

Validating a two-dimensional bipolar spectrum model integrating DSM-5's mixed features specifier for Major Depressive Disorder.

INTRODUCTION: The literature on DSM-5's 'Major Depressive Disorder with lifetime mixed features' (MDD-MF) is limited. This study investigated MDD-MF's potential inclusion into a bipolar spectrum. METHODS: We recruited 287 patients with Bipolar I disorder (BD-I), BD-II, MDD-MF or 'MDD without lifetime mixed features' (MDD-noMF); most (N=280) were stabilized for at least one year on medication. Sixteen validators (clinical features, psychiatric family history, temperament, stabilizing treatment) were compared across groups and subjected to trend analyses. Two discriminant function analyses (DFA; primary and secondary), excluding or including, respectively, treatment-related predictors, explored latent dimensions maximizing between-group discrimination; mahalanobis distances between group 'centroids' were calculated. RESULTS: Eleven validators differed significantly across groups; nine varied monotonically along a bipolar diathesis gradient with significant linear trends; two peaked at MDD-MF and displayed significant quadratic trends. In the primary DFA, apart from a classic bipolarity dimension, correlating with hospitalizations, early age at onset, lifetime psychosis and lower anxious temperament scores, on which groups ranked along a bipolar propensity gradient, a second dimension was also significant, peaking at BD-II and MDD-MF (challenging the classic bipolar ranking), which correlated with lifetime psychiatric comorbidities, suicidality, lower lifetime psychosis rates, female gender, higher cyclothymic and lower depressive temperament scores; MDD-MF was equipoised amidst BD-II and MDD-noMF. After including treatment-related predictors (secondary DFA), discrimination improved overall but BD-II and MDD-MF were closest than any other pair, suggesting similar treatment patterns for these two groups at this naturalistic setting. CONCLUSIONS: To our knowledge, this is the first time a two-dimensional bipolar spectrum based on classic external validators is proposed, fitting the data better than a unidimensional model. Additional predictors are warranted to improve BD-II/MDD-MF discrimination.

Posttraumatic stress disorder in outpatients with depression: Still a missed diagnosis.

Comorbidity between major depressive disorder (MDD) and posttraumatic stress disorder (PTSD) is a well-established fact but has been studied little among MDD patients and even less among outpatients. We assessed the prevalence and characteristics of comorbid MDD-PTSD patients in a sample of MDD outpatients in an effort to elucidate possible causes of MDD-PTSD comorbidity. A semistructured clinical interview was applied to 101 outpatients with MDD. Sociodemographic factors, psychiatric history, the presence of PTSD, and MDD-PTSD comorbidity were recorded. The prevalence of MDD-PTSD comorbidity was 38.6%, with 26.7% suffering currently from PTSD. The average duration of PTSD was 16 years, and in most cases (79.5%) PTSD started earlier than or simultaneously with MDD. Only 28.8% of patients with PTSD had a documented diagnosis in their medical record. The most significant factors predicting MDD-PTSD comorbidity were found to be chronic depression, a history of prolonged or repeated trauma, male gender, a younger age at onset of psychological symptoms, lower education, and a lower level of functioning. Our findings indicate that MDD-PTSD comorbidity still remains an overlooked fact. Prolonged trauma seems to be a major risk factor for MDD-PTSD comorbidity, predisposing subjects to PTSD and later on or simultaneously to comorbidity with MDD.

Psychoticism in patients with panic disorder with or without comorbid agoraphobia.

OBJECTIVE: A few case-reports have previously described transient psychotic-like symptoms in non-psychotic patients with panic disorder (PD). We aimed to systematically explore whether PD patients without any current or past psychosis can be differentiated according to the severity of 'psychoticism' as a dimension, comprising clinical features such as psychotic-like experiences, increased social alienation, hostility and suspiciousness. METHODS: Sample included 35 (female = 26) medication-free, non-psychotic patients consecutively referred from our Department's Outpatient Clinic for acute symptoms of DSM-5 PD with (PDA; N = 29) or without concurrent agoraphobia. Psychometric measures included the Symptom Checklist-90-Revised (SCL-90-R), Agoraphobic Cognitions Questionnaire (ACQ), Body Sensations Questionnaire (BSQ), and panic attacks during last 21 days PA-21d. RESULTS: Multiple regression analysis (forward stepwise) revealed that, among all SCL-90-R subscales, the psychoticism-subscale was most significantly associated with panic-related beliefs included in the ACQ, while significant associations emerged between the paranoid ideation-subscale and the ACQ and BSQ measures. Moreover, significant correlations emerged between the SCL-90-R psychoticism-subscale and all three measures of PD symptoms (ACQ, BSQ, PA-21d) and between the SCL-90-R paranoid ideation-subscale and both the ACQ and BSQ. CONCLUSIONS: This significant association between levels of psychoticism and severity of panic symptoms may reflect a more severe subtype of PD.

Retinal and choroidal alterations in patients with anorexia nervosa without vision loss.

OBJECTIVE: Evaluate the alterations of retinal anatomy and function, as well as choroidal thickness changes, in patients with anorexia nervosa (AN). METHOD: 13 female AN patients (26 eyes) and 20 female controls (40 eyes) were included. Assessment of the retinal and choroidal anatomy was performed by optical-coherence-tomography, while multifocal-electroretinogram was used for measurements of the electrical activity of the macula. Statistical analysis was performed using t-test. RESULTS: Central macular thickness was found to be thinner in AN (140.04 ± 14.45, 150.85 ± 16.03, p = 0.007), likewise the ganglion cell complex and outer retinal layer (ORL) at most areas. ORL superiorly was thicker in AN (169.12 ± 2.55, 163.00 ± 8.70, p < 0.001), while retinal nerve fiber layer was not different between the two groups, except the inferior region (121.08 ± 18.52, 137.60 ± 7.30, p < 0.001). Choroidal thickness was evenly diminished in the anorectic group (p = 0.001-0.027). Multifocal-electroretinogram showed lower P1-retinal response density amplitude of ring 1 in AN (159.04 ± 60.83, 292.43 ± 11.59, p < 0.001), but no significant difference concerning the P1-response density amplitude of ring 2 (79.04 ± 21.89, 82.63 ± 9.10, p = 0.36). DISCUSSION: In AN patients, even without vision loss, significant changes occur in retinal and choroidal thickness, as well as in the electrical activity of the macula. However, this is a pilot study in a small sample that needs replication.

The association between smoking and psychopathology adjusted for body mass index and gender.

OBJECTIVE: This study examined the correlation between smoking habits and psychopathology status, as well as the impact of confounders such as body mass index and gender. METHOD: A total of 134 non-smokers and 152 smokers were enrolled in this study. We measured psychopathology features using Symptom Checklist 90-Revised. We ran logistic regression models testing the smoking-psychopathology association, controlling for body mass index and gender. RESULTS: Smoking was positively correlated with depression, interpersonal sensitivity, hostility, somatization, paranoid ideation and psychoticism (P<0.05). Adjusting for body mass index and gender, the results remained largely unchanged, with a slight independent effect of body mass index. CONCLUSIONS: Our data suggest that smoking is a stronger predictor of psychopathology than body mass index and gender.

Hypothesis: Is heroin a 'barrier' against cancer? A retrospective analysis of heroin-addicted individuals untreated for opioid dependence between 2001-2010.

PURPOSE: The findings of previous studies attracted our interest in searching and defining the percentage of deaths from cancer in 'heroin regular addicts' i.e. those who had never stopped taking the drug since they started. METHODS: The archives of the Greek Reitox Focal Point of the years 2001 to 2010 were retrospectively searched, focusing on the number of deaths from cancer of the regular heroin addicts. RESULTS: The records from 2,321 regular heroin addicts showed that none of them died from cancer. It seems that heroin might act as a "barrier" against cancer. CONCLUSION: Further studies are needed to confirm our results and to explore the potential cause for this surprising finding.

The Amount of Phosphorus in the Blood of Heroin Abusers Compared to that of Healthy Subjects.

BACKGROUND: The aim of the current retrospective study was to assess any difference in terms of serum phosphate (P) between heroin addicts and healthy subjects. METHODS: Between 2011 and 2012, under the authority of the Greek Organization Against Drugs (OKANA), 30 regular heroin addicts, 22 males and 8 females (Group A) participated at the study. Between 2010 and 2011, 30 healthy individuals, 22 males and 8 females (Group B), presented on an outpatient basis for either fatigue or common flu symptoms without fever at the 424 Military Hospital of Thessaloniki. RESULTS: No significant difference between group A and B, in terms of either age (p = 0.454, Mann-Whitney test) or male/female ratio (p = 0.573, Chi2 test), suggesting a homogeneity for the population of individuals participating in the study. The mean values of serum-P in group A and B were 3.47 ± 0.65 and 3.35 ± 0.58, respectively (p = 0.45, Mann Whitney test). CONCLUSIONS: The absence of statistical difference of serum-P between heroin addicts and healthy subjects as shown in our results should be confirmed in further studies.

Episodic Visual Learning/Memory and Attentional Flexibility in Patients With Major Depressive Disorder After Clinically Effective Electroconvulsive Therapy.

OBJECTIVES: This study is a follow-up of a previous one reporting that the neuropsychological profile of pharmacoresistant patients with major depressive disorder referred for electroconvulsive therapy (ECT, ECT group) contrasted with that of their pharmacorespondent counterparts (NECT group). The NECT group exhibited severe visuospatial memory and minor executive deficits; the ECT group presented the reverse pattern. In that same ECT group, the current follow-up study examined the effects of clinically effective ECT on both cognitive domains 2 months later. METHODS: Fifteen ECT patients were administered Hamilton Depression (HAMD-24), Hamilton Anxiety (HAMA), Mini-Mental State Examination Scales and 5 tests of Cambridge Neuropsychological Test Automated Battery at intake (pre-ECT), end of ECT course (post-ECT), and 2 months thereafter (follow-up). RESULTS: Electroconvulsive therapy was effective in relieving clinical depression. After a post-ECT decline, the patients exhibited significant improvement in both Cambridge Neuropsychological Test Automated Battery, paired associate learning, and Stockings of Cambridge. By contrast, their major pre-ECT deficit in intra/extradimensional set shifting remained virtually unaffected. CONCLUSIONS: Our findings suggest that attentional flexibility deficits may constitute a neuropsychological trait-like feature of pharmacoresistant, ECT-referred major depressive disorder patients. However, this deficit does not seem generalized, given patient improvement in episodic visual learning/memory and some indication of improvement in spatial planning after ECT.

Baseline heartbeat perception accuracy and short-term outcome of brief cognitive-behaviour therapy for panic disorder with agoraphobia.

BACKGROUND: Increased heartbeat perception accuracy (HBP-accuracy) may contribute to the pathogenesis of Panic Disorder (PD) without or with Agoraphobia (PDA). Extant research suggests that HBP-accuracy is a rather stable individual characteristic, moreover predictive of worse long-term outcome in PD/PDA patients. However, it remains still unexplored whether HBP-accuracy adversely affects patients' short-term outcome after structured cognitive behaviour therapy (CBT) for PD/PDA. AIM: To explore the potential association between HBP-accuracy and the short-term outcome of a structured brief-CBT for the acute treatment of PDA. METHOD: We assessed baseline HBP-accuracy using the "mental tracking" paradigm in 25 consecutive medication-free, CBT-naive PDA patients. Patients then underwent a structured, protocol-based, 8-session CBT by the same therapist. Outcome measures included the number of panic attacks during the past week, the Agoraphobic Cognitions Questionnaire (ACQ), and the Mobility Inventory-Alone subscale (MI-alone). RESULTS: No association emerged between baseline HBP-accuracy and posttreatment changes concerning number of panic attacks. Moreover, higher baseline HBP-accuracy was associated with significantly larger reductions in the scores of the ACQ and the MI-alone scales. CONCLUSION: Our results suggest that in PDA patients undergoing structured brief-CBT for the acute treatment of their symptoms, higher baseline HBP-accuracy is not associated with worse short-term outcome concerning panic attacks. Furthermore, higher baseline HBP-accuracy may be associated with enhanced therapeutic gains in agoraphobic cognitions and behaviours.

Can cognitive deficits differentiate between schizophrenia with and without obsessive-compulsive symptoms?

BACKGROUND: The frequent occurrence of obsessive-compulsive symptoms (OCS) in the course of schizophrenia and their impact on the functional outcome of the illness underlie the suggestion that the presence of OCS represents a separate subtype of schizophrenia, with a distinct clinical presentation and prognosis and specific neurobiological characteristics. This study investigated whether the presence of OCS in schizophrenia is associated with worse cognitive functioning in the domains of processing speed, executive functions and visuospatial memory. We also explored whether the degree of impairment in any of these cognitive domains could predict group membership (i.e. Schizophrenia with OCS [Sch-OCS] and Schizophrenia without OCS) and if there was a relationship between cognitive functioning and severity of OCS within the Sch-OCS group. METHODS: Forty patients with schizophrenia, 20 with and 20 without OCS, individually matched for age, gender, years of education and severity of psychotic symptoms and 20 healthy controls underwent a comprehensive neuropsychological assessment. RESULTS: Only lower performance in processing speed discriminated patients with OCS from patients without OCS. Processing speed impairment not only classified patients in OCS or non-OCS group but was also independent of the severity of OCS symptoms. CONCLUSIONS: The notion of additive effects of both schizophrenia and OCD on the structural and functional integrity of the brain circuits that support cognitive functions warrants further investigation in longitudinal neuropsychological and neuroimaging studies with larger samples and sufficient variation in the severity of OCS.

mPD: Introduction of a single player prisoner's dilemma application for medical experiments.

BACKGROUND: Prisoner's dilemma is one of the most popular concepts among scientific literature. In medical literature the majority of prisoner's dilemma experiments with human participants implement computerized means. Despite this, there is no shared validated tool for prisoner's dilemma tasks. METHODS: The application is developed in Javascript programming language and makes use of the pixijs library for WebGL rendering. To create a custom trial, a set of variables have to be set. These refer to the linguistics, user controls, available choices, computer strategy, interaction flow (simultaneous or sequential), opponent's choice prediction requirement, noise induction, human opponent behavior simulation, the way resulted data will be handled and more. Results are in JSON format and include time interval data. RESULTS: We have developed an application which, given the various parameters experimenter can modify, is able to simulate a large number of single player prisoner's dilemma versions. It is open source with no installation requirement, executable by any modern internet browser remotely or locally with the ability to post data results either locally or remotely. Experimenter only has to modify certain starting values in order to create his design of choice. Two examples are included, with initial settings and results, to demonstrate the use and validity of the application. CONCLUSIONS: Our aim is to assist future researchers in their methodological designs. In this scope, our application, has the minimum requirements, can be served either locally or remotely, has a wide range of modifiable parameters and takes care of the resulted data. In the long term, a shared and validated tool would contribute to increasing methodologies' credibility and mitigating cross-validation discrepancies.