The pioneering work of Ödegaard (1932) was the first to link migration and schizophrenia by reporting rates in Norwegian immigrants in Minnesota as twice that of native Minnesotans and of Norwegians in Norway. However, only in recent decades has an interest in migration and schizophrenia been rekindled as a result of reports of elevated rates of schizophrenia in Afro-Caribbean immigrants in the United Kingdom in the mid- 1960s (Hutchinson & Haasen, 2004). Later studies reported elevated rates in secondgeneration Afro-Caribbean immigrants compared to first-generation (Harrison, Owens, Holton, Neilson, & Boot, 1988). In the United States, Blacks were diagnosed with schizophrenia 2.4 times more often than Whites (Olbert, Nagendra, & Buck, 2018). However, mental health researchers in the United States generally combine all individuals of African descent as African- Americans. This practice obscures the nuances of culture and ethnicity within the Black subgroups as well as the immigrant status of Afro-Caribbeans. This research focused on the Afro-Caribbean immigrants and factors that predict risk for schizophrenia within this population. The process of migration is a complex enterprise that produces stressors and challenges, the effects of which are multifaceted. The social and environmental forces that parallel the process of migration may predispose individuals to severe psychiatric disorders such as schizophrenia. Socio-political dynamics in the host country that marginalize others of different cultural and/or racial persuasions can compound the negative effects of post-migration. Therefore, migration is considered a social determinant of health. Empirical evidence has substantiated that socio-environmental factors such as urbanicity, discrimination or socio-economic deprivation, social support, and goal striving stress are potential contributing factors to the development of psychotic disorders in immigrants. Moreover, evidence has supported that the darker the skin color of the immigrant the greater the risk (Cantor-Graae, 2007). The findings of this study confirmed that for Afro-Caribbean immigrants stressors in the post-migration phase such as discrimination, limited social support, and economic hardship that can be compounded by the number of dependent children were identified as possible predictors of risk for schizophrenia. This risk increased with length of residency and continued into the second-generation. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

(Truncated abstract) The aims of this thesis are: (i) To estimate the prevalence of psychiatric illness among persons with intellectual disability and, conversely, the prevalence of intellectual disability among persons with a psychiatric illness; (ii) To describe the disability and service utilisation profile of persons with conjoint disorder; (iii) To examine, in particular, intellectual disability co-occurring with schizophrenia; and (iv) To explore the role of hereditary and environmental (specifically obstetric) risk factors in the aetiology of (i) intellectual disability and (ii) intellectual disability co-occurring with psychiatric illness. This thesis has a special interest in the relationship between intellectual disability and schizophrenia. Where data and sample sizes permit, it explores that relationship at some depth and has included sections on the putative nature of the link between intellectual disability and schizophrenia in the introductory and discussion chapters. To realise its objectives, the thesis comprises a core study focusing on aims (i) – (iii) and a supplementary study whose focus is aim (iv). It also draws on work from an ancillary study completed prior to the period of candidacy...This thesis found that, overall, 31.7% of persons with an intellectual disability had a psychiatric illness; 1.8% of persons with a psychiatric illness had an intellectual disability. The rate of schizophrenia, but not bipolar disorder or unipolar major depression, was greatly increased among cases of conjoint disorder: depending on birth cohort, 3.7-5.2% of individuals with intellectual disability had co-occurring schizophrenia. Down syndrome was much less prevalent among conjoint disorder cases despite being the most predominant cause of intellectual disability while pervasive developmental disorder was over-represented. Persons with conjoint disorder had a more severe clinical profile including higher mortality rates than those with a single disability. The supplementary study confirmed the findings in the core body of work with respect to the extent of conjoint disorder, its severity, and its relationship with pervasive development disorder and Down syndrome. Moreover, the supplementary study and the ancillary influenza study indicated a role for neurodevelopmental insults including obstetric complications in the adverse neuropsychiatric outcomes, with timing of the insult a potentially critical element in defining the specific outcome. The supplementary study also added new information on familiality in intellectual disability. It found that, in addition to parental intellectual disability status and exposure to labour and delivery complications at birth, parental psychiatric status was an independent predictor of intellectual disability in offspring as well as a predictor of conjoint disorder. In conclusion, the facility to collect and integrate records held by separate State administrative health jurisdictions, and to analyse them within the one database has had a marked impact on the capacity for this thesis to estimate the prevalence of conjoint disorder among intellectually disabled and psychiatric populations, and to understand more about its clinical manifestations and aetiological underpinnings.