The six schools of theories (psychodynamic, behavioral, cognitive, social, existential and biological) forms the foundation of current day practice for prevention and management of mental disorder [1]. In sociology, mental illness is a deviant behaviour resulted from problem in thoughts, feelings and cognition which is not appropriate for surrounding environment. The positive aspect of such model is that it is based on cultural/social context but the negative aspect is that such approach leads to generalization which is often not the case, as individuals vary from one another in many aspects [2]. However it creates a window for intervention in society to prevent genesis of mental disorder in large number of individual living in that society. Sociological theories widens the concept of mental disorder to include the conditions of life, individuality, structure of power and dominance in a society, government policies for resource allocation [3]. Thus, research in the sociology of mental health is essential for grounding, refining, challenging, or modifying the conceptions of social theorists.

The important sociological theories, which have revolutionary effects in defining mental disorder, are functionalism theory, interpersonal theory, attachment theory, and stress theory, labeling theory, social class, migration and urbanization. According to functionalism theory all elements of a society forms a well-defined ecosystem, any change in one element, destabilizes the whole ecosystem, and then society alter itself to re-stabilize the ecosystem. However, if society changes too fast, it become impossible to re-stabilize the ecosystem and then it enters in to anomie or normlessness, which weakens its collective conscience and create anomic society [2,4]. The individual start feeling alienation (feeling of powerless, meaningless, normless, isolated and self-estranged) i.e. person does not feel that he is a part of the whole societal ecosystem [5]. The alienated person is "empty and depressed" [6]. The Interpersonal Theory is principally based on needs (needs for satisfaction and security) and anxiety. Anxiety occurs when fundamental needs are in danger of not being met. According to this theory needs acts as primary motivator of human behavior. That is also the major set-back for this theory because this theory ignores instinctual life and its role in development of child completely [7]. He believed that infant biological needs evoke tenderness in mother. Her tender gratification of infantile urges brings about relief of tension and feeling of security, which helps in building the self-esteem of child. If anxiety interferes with tenderness in mother, this anxiety imparted directly in to children leading to insecurity, low self-esteem and increased vulnerability to mental illness [7]. He regards anxiety as purely psychogenic and quite mystic in origin, the outcome of child’s first interpersonal relationship.

Attachment Theory: According to this theory, human instinct forms a strong and persistent affectional attachment bond with other objects. Loss of such affectional attachment bonds causes development of intense anxiety, restlessness as a behavioral change in individual. This behaviour tries to recoup the lost attachment bond and relationship with object. According to this theory the infant-mother attachment bond is prototype of such attachment bond. There are 4 types of attachment bonds, Secure- The individual is able to give and receive care. The care is provided, when needed, Anxious- ambivalent-Individuals are never sure that their attachment needs will be met; believe that care must be sought constantly, Anxious -Resistant: attachment needs are provided but individual reject it, Anxious-avoidant- the individual behaves as if other will never provide care, when needed. The quality of attachment bond in childhood, influence though, feeling, behavior and shapes the cognitive and emotional development in adults. It has been observed that series of disorganized attachment interaction along developmental path of children increases risk of developing borderline personality disorder [8] and eating disorder [9]. Research on attachment theory required to understand the mechanism of development of psychiatric disorder due to disorganized attachment bonding.

Stress theory: The “nonspecific response of body to any demand caused by either pleasant or unpleasant condition”. Stress has direct relation with either genesis and prognosis of mental disorder [10,11,12]. There is enough evidence that stress has epigenetic effect i.e. it affect DNA methylation (expression of genes) resulting in increased chances of developing psychiatric disorder [13]. It provide direct link of sociological theory with biological theory of mental disorder. According to Labeling theory people, who are labeled as deviant, treated as deviant eventually become deviant. Socioeconomic condition play a significant role in labeling as deviant because people with higher socio-economic status have higher control over society. People with deviant behaviour are blocked to access normal life and needs. Furthermore these individuals develop secondary deviance, become socialized to mental- patient culture and continue to live with abnormal behavior [14]. Bruce Link in 1987 proposed modified labeling theory, which state that stigmatised individuals recognise the negative label applied on them have projected their role in society as less intelligent, trust worthy and more dangerous and incompetent. This type of thinking decreases their self-esteem and self-efficacy and eventually restricts them from social participation. People with mental disorder are generally labeled as deviant, unpredictable, violent, disruptive, dangerous and incurable. This theory sensitizes mental health professional about stigma of mental illness and danger of institutionalization. Social class-this theory gave the special importance to social class are social causation hypothesis and social drift hypothesis. According to Social causation hypothesis, the prevalence of mental illness is higher in lower socioeconomic status group due higher psychological stress produced by environmental adversity (such as unemployment and poverty, social disadvantage, homelessness). According to Social drift hypothesis, person with mental illness of those who have trait that predisposes to mental illness drift down in to or unable to rise from lower socioeconomic status [18,19]. Migration-Migration is a universal phenomenon, which existed with the subsistence of the human beings on earth. People migrate from one place to another for several reasons, but the goal or main reason behind changing the residence would be improving their living conditions or to escape from debts and poverty. Several factors like language barriers, concerns about legal status, difficulties related to acculturation, racism, isolation, housing, and health problems leads increases the risk of mental health problems after settlement in host countries. Studies have reported that around 24% of migrant women in cities are mentally unhealthy and around 50 % migrant population develops at least one psychiatric symptoms [20,21]. Migrant population have found increased rates of schizophrenia, depression, anxiety disorders, and other psychiatric disorders than general population. The increased frequency of mental disorders in migrants can be explained due to development of sense of insecurity, low self‑esteem, non-availability of member of their own community changing concepts of self, their role in society, and mismatch between aspiration and achievements [22]. Urbanization-Urbanization, defined as the increase in the number of cities, urban population and industrialization, is not only a demographic movement but also includes, social, economic and psychological changes that constitute the demographic movement. Urbanization is promotes individualism, weakens the collective conscience of society. Urbanization affects mental health through the influence of increased stressors and factors such as overcrowded and polluted environment, high levels of violence, and reduced social support [23]. This is responsible for increase in frequency of mental disorder such as psychoses, depression, substance abuse, crime, delinquency, vandalism, family disintegration. There are studies, which have shown the direct association of urbanization and increase in prevalence of schizophrenia [24,25].

Prevention for mental disorder
This paper will provide a brief review of primary prevention for various psychiatric disorders. Primary prevention includes universal, selective and indicated prevention. Universal prevention focus whole population irrespective of risk factors, Selective prevention focus on a subgroup of population with increased risk for mental disorder as evidenced by biological and psychosocial factor and Indicated prevention targets people with detectable sign and symptoms of mental disorder.

Addressing risk and protective factors for mental disorder: Risk factors are associated with an increased probability of onset, greater severity or longer duration of major psychiatric problems. Protective factors refer to conditions that strengthen the people against those factors, which are associated with increased risk of mental disorder and also ameliorate or modify the course of mental illness [26].