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Psychiatric disorders may co-occur in the same individual. These include, for example, substance abuse or obsessive-compulsive disorder with schizophrenia, and movement disorders or epilepsy with affective dysfunctional states. Medications may produce iatrogenic effects, for example cognitive impairments that co-occur with the residual symptoms of the primary disorder being treated. The observation of comorbid disorders in some cases may reflect diagnostic overlap. Impulsivity, impulsiveness or impulsive behaviour is implicated in a range of diagnostic conditions including substance abuse, affective disorder and obsessive-compulsive disorder. These observations suggest a need to re-evaluate established diagnostic criteria and disorder definitions, focusing instead on symptoms and symptom-profiles.

Les mécanismes neuropsychologiques sous-jacents à l’expression symptomatique du trouble obsessionnel compulsif (TOC) sont encore mal connus. Nombreuses sont les études qui mettent en évidence des déficits exécutifs mais la diversité des méthodologies et la mixité des sous-types cliniques empêchent de dégager des constantes en terme de profil neurocognitif. Les études neuropsychologiques accordent toutefois une importance à l’inhibition et à flexibilité cognitive qui pourraient participer au caractère inflexible et répétitif des pensées et des actes communs à toutes les formes du TOC. L’objectif de cette thèse est l’étude des mécanismes d’inhibition et de la flexibilité chez des patients présentant un TOC. Deux études ont été réalisées. L’étude 1 est une étude de faisabilité d’un protocole de tests neuropsychologiques où 9 patients sont comparés à 9 sujets contrôles. L’étude a fait l’objet d’une bonne faisabilité. L’étude 2 compare 14 patients présentant un TOC à 16 patients présentant des troubles phobiques avec des tests informatisés d’inhibition, de flexibilité en plus des tests de l’étude 1. Les objectifs sont : vérifier l’hypothèse d’un déficit d’inhibition chez des patients TOC, étudier les relations entre la sévérité, l’ancienneté des troubles TOC et les résultats aux tests d’inhibition et de flexibilité. Les limites méthodologiques, entre autre, l’absence d’un groupe contrôle réduisent l’interprétation comparant les deux groupes cliniques ainsi que les résultats au sein du groupe de patients TOC. Les patients se sont différenciés sur deux épreuves de rapidité d’exécution en flexibilité mentale et d’attention. Au sein du groupe des patients présentant un TOC, les données ont montré une relation entre la sévérité des symptômes TOC et des perturbations aux tests d’inhibition. Ces observations sont discutées en lien avec le concept « impulsivité et TOC » / The nature of neuropsychological mechanisms underlying clinical picture of obsessive-compulsive disorders (OCD) has not, as yet, been clearly determined. Number of studies has emphasized the role of cognitive deficits, but diversity of methodology and overlapping of clinical sub-groups, did not allow establishing specific neuro-cognitive profile. Neuropsychological studies recognize, however, the place of inhibition and alteration of cognitive flexibility that could be at origins of inflexible and repetitive nature of thoughts and actions, typical of all obsessive-compulsive disorders. The aim of this thesis was to explore the mechanisms of inhibition and cognitive flexibility in patients with OCD. Two studies were carried out. In the first, pilot study, we wanted to verify the feasibility of neuropsychological tests comparing 9 OCD patients with 9 controls. The study demonstrated a good feasibility. In the second, 14 OCD patients were compared to 16 phobics, using computerized tests of inhibition and flexibility, in addition to a battery used in the first study. The objectives were to verify hypothesis of inhibition deficit in patients with OCD, to examine relationship between severity and length of OCD and the results on neuropsychological tests of inhibition and flexibility. Methodological limits with, amongst other, the absence of control group, diminish predictive value of the comparison of two clinical groups as well as between patients with OCD. However, we found differences between patients in two tests, the one of rapidity of execution in mental flexibility and the other of attention. In the group of patients with OCD, data indicated relationship between severity of symptoms of OCD and their results on tests of inhibition. These data are further discussed in terms of relationship between “impulsivity and OCD”

Acceptance and commitment therapy (ACT) has been used with promising results for adults with obsessive-compulsive disorder (OCD). There are currently no published studies utilizing ACT for pediatric OCD. An investigative pilot study utilizing a nonconcurrent multiple baseline design examined the extent of treatment effects when ACT is employed for pediatric OCD. Three children under the age of 12 were enrolled in a nine-session ACT treatment protocol. The primary dependent variable was number of obsessive cognitions as recorded by participants within a participant-observer framework. Treatment response was also evaluated using the Children’s Yale-Brown Obsessive Compulsive Scale (CY-BOCS). Results indicated that two of three participants successfully responded to treatment as evidenced by significant reductions in selfobserved frequency of obsessive cognitions. Results further indicated large reductions for all participants on the CY-BOCS with a mean score decrease of 47.26%. Implications and future directions were considered. The research yielded results that indicated that ACT may be useful in the treatment of pediatric OCD and that further research is warranted.

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The 5-HT agonist drug mCPP contributed to a 5-HT hypothesis of obsessive-compulsive disorder (OCD), but the effects of the drug in human and animal studies have been inconsistent. The objective of this thesis was to shed light on the behavioural and neurobiological effects of mCPP using the quinpirole sensitization rat model of OCD and in a reciprocal manner, to use the drug to further reveal behavioural and neurobiological components of the animal model. The utility in using the quinpirole model is that the process of analysis by experimentation can be employed to observe effects of the drug on three separate behavioural components identified to underlie the model compulsive behaviour: vigor, focus and satiety. Four original studies were designed to address this objective, and the findings yielded novel contributions to the literature. We suggest that mCPP attenuates compulsive checking by attenuating the exacerbated vigor and satiety characteristic of compulsive behavior, but this effect may not have been captured in previous clinical studies because OCD was measured as a unitary phenomenon across different symptom subtypes. We also reveal that separate systems underlie the development and performance of compulsive behaviour in the animal model, and mCPP reduces its performance but not its development. Hence, the animal model findings suggest that mCPP can attenuate performance of OCD behavior but the drug does not reverse the pathology of OCD or arrest the pathogenesis of OCD. Neurobiologically, we hypothesize that the underlying mechanism mediating the response to mCPP is mediated downstream of the nucleus accumbens core (NAc), at the substantia nigra pars reticulata, based on the finding that the effects of mCPP on vigor and satiety are present in NAc lesioned animals. Finally, although findings of this thesis indicate that 5-HT2A/C receptors do not mediate the response to mCPP, an oppositional role for DA and 5-HT on the model of compulsive behaviour is proposed, consistent with a security motivation theory of OCD. Overall, this thesis shed new light on the effects of mCPP on OCD, and reveals novel neurobiological and behavioural correlates of the quinpirole model. / Thesis / Doctor of Philosophy (PhD)

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Although forgiveness has been associated with reduced anxiety in several studies, and Obsessive-Compulsive Disorder is an anxiety disorder, the potential association between forgiveness and obsessive-compulsiveness has been generally unexplored. The current study examined the association between three dimensions of forgiveness and obsessive-compulsive (OC) symptoms as mediated by locus of control (LOC) in a college student sample (N = 241). Forgiveness of self (FS) and of others, but not feeling forgiven by God, were associated with overall OC symptoms and with a majority of symptom subscales. LOC was limited in its role as a mediator that was restricted to associations with FS. Furthermore, LOC-Chance was the only dimension found to be a specific mediator, as control attributed internally and to powerful others did not mediate any of the forgiveness-OC associations. These findings are discussed in the context of both past and future research related to forgiveness, obsessive-compulsiveness, and control constructs.