Globally, the number of international migrants has increased steadily from 173 million in 2000 to 258 million in 2017. The majority of all international immigrants reside in Asia, while North America hosts the third largest number of migrants. The relationship between international migration and development has received increasing attention since the International Conference on Population and Development in 1994, and many migration-related goals have been included in the United Nations Sustainable Development agenda for 2030. Migration is key in achieving the Sustainable Development Goals as it is transformative for the individual, the host countries, and the origin countries.
Depression is a leading cause of disability globally with a lifetime prevalence of 12.9% . Depression is strongly linked with suicide, and suicide is a leading cause of death among young people . A recent meta-analysis of 25 studies reported the prevalence of depression among immigrants of different nationalities to be 15.6% . The association between migration and depression is controversial because previous studies have found the link to be inconsistent [6, 7]. A systematic review of mental health among immigrants by Bas-Sarmiento et al., has reported that although migration is a significant stressor for mental disorders, it does not exclusively lead to mental distress . Other factors such as gender, marital status, length of stay in the host country, social support and employment status are significant risk factors for developing mental disorders .
In recent years, a large number of black African-born immigrants have migrated to Canada. Amongst this group, those from Nigeria make up the largest percentage. Nigeria is home to the largest population of blacks in the world, and the lifetime prevalence of major depressive episode amongst its adult population is 3.1%. Canada is an attractive destination for a lot of Nigerians as it presents economic opportunities in sectors like as oil and gas, ICT, health care, and other STEM-related fields which appeal to Nigerian professionals . In 2019, a total of 12, 595 Nigerians migrated to Canada making them the fourth-leading population of new immigrants in Canada . Educational opportunities are also a popular reason for migrating to Canada. About 12,000 Nigerians are currently studying in Canada, and are well-positioned for conversion into permanent resident status because they can leverage their youth, English language fluency, Canadian education, and Canadian work experience .
Previous studies have reported a ‘healthy immigrant paradox’ in Canada . However, this contrasts with other reports where immigrants who have migrated from low- and middle-income countries to high-income countries have been shown to exhibit higher risks of depression relative to their host populations. This indecisive findings necessitates further study.
In this study, the negative effect of immigration due to acculturative stress will guide the understanding of the prevalence and predictors of depression among immigrant Nigerians. An important premise of acculturative stress is that immigration is a significant stressor, and the lifestyle changes and adjustments associated with migration could increase health risks . Contributing factors to poor health and mental disorders among immigrants include; living conditions and endemic diseases in immigrants’ countries of origin; social, political, and environmental conditions associated with the immigration process; and social isolation, cultural conflicts, poor social integration and social support, low socioeconomic status, and racial discrimination [13, 14]. Low levels of social support have been associated with depression in previous studies among Nigerians [15–18]. Nigerian immigrants living in new immigrant destinations may be unable to receive support from family members thus, may be susceptible to depression. Interestingly, in a qualitative study of depression among immigrant Nigerian men in the United States of America, the participants denied the existence of depression and claimed that depression did not exist in the Nigerian culture . Immigrant Nigerian women also had similar beliefs as they also thought that depression was something that affected other people and associated it with spirituality and possession by evil spirits . However, this does not imply that depression does not exist- for instance, Gureje et al.  reported that the lifetime prevalence of major depressive episode among adult Nigerians is 3.1%.
Immigrant Nigerians in Canada are an understudied population for whom the prevalence of depression and its associated factors are not known. Considering the increasing population of Nigerians migrating to Canada, it is important to explore the predisposing factors that may lead to depression among them. The study of depression among Nigerian immigrants is particularly relevant as mental disorders are known to be higher among migrant populations compared to native populations [10, 21]. Promoting good mental health amongst immigrant population is a key concern for policymakers in Canada. In recent years, the number of permanent resident immigrants to Canada has increased, with immigrants from Asian countries (India, China and Philippines) ranked top three, while Nigeria is ranked 4th. Due to deeply-rooted socio-cultural influences in the country of origin of the immigrants, a study on depression among migrants should accommodate contextual differences, hence should be contingent on a homogenous immigrant population. While information on depression among Asian migrants, including those from India, China and Philippines, in Canada have been reported in previous studies[23, 24], there is inadequate information about depression among Nigerian immigrants who make up the largest percentage of African migrants and black population residing in Canada. The present study aimed to assess the prevalence of depression among Nigerian immigrants in Canada, and the predictors of depression among them.