Mental health is defined as the capacity to work, capacity to love and the capacity to play and for recreation [1]. Approximately one in five of the world's youth, 15 years and younger suffer from mild to severe mental disorders. A large number of these children remain undetected and untreated [2]. It must be noted that mental health is one of the more recently added components of Primary Health Care (PHC) and means more than merely the presence or absence of obvious mental illness. In Nigeria 28.5% of those attending primary care setting in an urban area were found to have psychiatric morbidity [3, 4]. The disintegration of the traditional, extended family due to factors such as economic migration inevitably creates socio-cultural changes that may affect the mental health of the individuals in the society. Furthermore, concerns for job security and the economic survival of the household can create enormous pressure on individuals which may in turn affect their mental health [5, 6].

Available studies have been largely facility-based, while community- based studies have been very scanty. Several studies have been done using general health questionnaire (GHQ12) as a tool for screening mental illness in developed countries where the prevalence of psychiatric morbidity ranges between 17%–25% [6–8]. This study assessed the prevalence of and factors associated with mental illness in Oyo State at community level using the general health questionnaire as a screening tool. The public health significance of this study is that it will provide a conceptual framework for addressing mental health promotion goals. It also offers a highly appropriate framework through which community-based mental health activities could be addressed. Moreover, it could also be used for health planning and practice.

The study was carried out in Oyo State one of the 36 states in Nigeria. This community based study is cross sectional in design and aimed at collecting data on mental health in rural and urban Oyo State, Nigeria.

This study examined the prevalence of psychiatric morbidity in the urban and rural areas of Oyo state with a view to identify the factors that are associated with mental illness in the general population at the community level. The overall prevalence of psychiatric morbidity found at the community level in this study was 21.9%. It is however slightly higher than what is found in other community-based surveys carried out in developed countries such as Spain, Canada, Norway and Australia [9–11].

The prevalence of psychiatric morbidity in the rural area was found to be significantly higher than the prevalence in the urban location. This is contrary to what was found in similar studies carried out in developed countries such as Great Britain where mental disorder was commoner in the urban areas than in the rural population [12]. The adolescent age group was found to have higher psychiatric morbidity when compared to the adults. Similar observations have been made in several studies [21, 22]. The adolescent period is a turbulent period in life when there is transition into adulthood and self autonomy. This may explain the higher morbidity rates [23].

The study underlines the effect of family structure on the mental health of the population. Marriage was found to be associated with mental stability in Oyo state. Those separated from their spouses, divorcees and widows had a higher mental morbidity. Sticking to acceptable family structures may create mental tension in the communities studied. Aspiration to meet up to the community standards is usually a common source of mental stress. [14, 15]. The indigenes were found to be more mentally stable than non-indigenes showing that migrants in Nigeria may be predisposed to setbacks psychologically when compared with the indigenes. This needs however to be further investigated as this is contrary to research done among Canadian Chinese migrants which shows that they do not suffer mentally compared with the general Chinese population [15].

Large family size and Unemployment was found to be associated with increase in psychiatric morbidity. This study corroborates the findings of several authors who found out that the larger the size of the family the lower the quality of child upbringing. This may lead to delinquent behavior among the children and increased mental stress on the care providers [16, 17]. Unemployment is an important risk factor for mental illness and a significant determinant in the development of mental pathology especially among the adolescents [18]. However among those with employment the professionals had the highest morbidity rate. The possible reason for this in a Nigerian population is not immediately clear. Those with high level of formal education had higher psychiatric morbidity rate in the Nigerian community. This is similar to the conclusion of many authors [19, 20].

This study shows that prevalence of psychiatric morbidity is high in Oyo state, Nigeria and slightly higher than what is obtained in the community- based studies in the developed countries. The rural population is in greater need of mental health promotional services. Basic essential needs provided by the government in both rural and urban areas especially made available to the younger generation and promotion of family planning to reduce family size would help to reduce psychiatric morbidity and improve quality of life in this African population.