Dopaminergic mechanisms underlying psychosis

Schizophrenia is a potentially devastating mental illness with a complex aetiology, in which the odds ratios for environmental risk factors for the disorder are greater than the odds ratios of any single gene hitherto identified. Within schizophrenia, striatal dopamine dysfunction has been proposed to underlie the development of psychosis. The Aberrant Salience hypothesis provides an explanatory model based on empirical findings to explain how psychotic symptoms may arise from striatal hyperdopaminergia, whereby multiple risk factors converge to elevate striatal dopamine synthesis capacity as the Final Common Pathway to psychosis. Two important epidemiological risk factors for the disorder are chronic cannabis use and longterm psychosocial stress, both of which have evidence supporting effects on the dopamine system. Environmental risk factors are by their very nature modifiable, and so this thesis examined whether these environmental risk factors were associated with the same dopaminergic abnormalities that have been observed in schizophrenia with 3,4-dihydroxy-6- [18F]-fluoro-l-phenylalanine Positron Emission Tomography. This thesis also examined whether cannabis users exhibit aberrant salience processing using a behavioural task, the Salience Attribution Task. This thesis found that long-term cannabis use was associated with reduced dopamine synthesis capacity and no relationship was found between striatal dopamine synthesis capacity and cannabis-induced psychotic-like symptoms. Whilst cannabis use was not associated with increased aberrant salience processing, there was a relationship between cannabis-induced psychotic-like symptoms and aberrant salience processing. This thesis found that long-term psychosocial stress is associated with reduced dopamine synthesis capacity, although this finding may be due confounding factors. However, a positive relationship was observed between childhood and recent adult stressors and dopamine synthesis capacity. These findings call into question the hypothesis that cannabis increases the risk of psychosis by inducing the same changes observed in schizophrenia, although there some evidence to support the hypothesis that psychosocial stressors do increase risk via this mechanism.Open Acces

Developmental variables of undergraduate resident assistants when negotiating conflict with peers.

The role of the Resident Assistant (RA) has assumed special prominence during the last thirty years, as theories of student development have promoted the practice of peer education, particularly in residence halls. RAs have been given a long list of tasks and job expectations that can be generally categorized within peer counseling and policy enforcing functions. Some researchers and writers in the field of student development and residence hall ecology have argued that with proper training and supervision, RAs can adequately fulfill their assigned duties while simultaneously matriculate, fulfilling their own personal undergraduate academic and social needs. This assumption is presently under scrutiny, as information from cognitive development regarding late adolescent epistemology questions the readiness of these students to be able to perform simultaneously in all of their roles. In particular, the role of enforcing university rules and regulations with many floormates who are also peers and friends presents RAs with levels of conflict that may stem from their current cognitive developmental level, thus limiting the ways they negotiate conflict during enforcement activities. The result may be a mis-match of person to task. Some undergraduate RAs may not be ready to carry out their most developmentally challenging task of enforcing campus policy with peers to whom they have ties of support and friendship. The purpose of this study is to investigate the possibility of certain behavioral trends in the ways RAs negotiate conflict with their peers while enforcing university policy based on their tested cognitive developmental level. By administering two production-type developmental assessments and one preference-type conflict mode inventory, as well as performing individual interviews of selected RAs, I examine possible mis-matches and matches of RAs with their roles, particularly that of policy enforcement with peers