Causes

Main article: Causes of mental disorders

Mental disorders can arise from a combination of sources. In many cases there is no single accepted or consistent cause currently established. A common belief even to this day is that disorders result from genetic vulnerabilities exposed by environmental stressors. (see Diathesis-stress model). However, it is clear enough from a simple statistical analysis across the whole spectrum of mental health disorders at least in western cultures that there is a strong relationship between the various forms of severe and complex mental disorder in adulthood and the abuse (physical, sexual or emotional) or neglect of children during the developmental years. Child sexual abuse alone plays a significant role in the causation of a significant percentage of all mental disorders in adult females, most notable examples being eating disorders and borderline personality disorder.
An eclectic or pluralistic mix of models may be used to explain particular disorders, and the primary paradigm of contemporary mainstream Western psychiatry is said to be the biopsychosocial (BPS) model, incorporating biological, psychological and social factors, although this may not always be applied in practice. Biopsychiatry has tended to follow a biomedical model, focusing on "organic" or "hardware" pathology of the brain. Psychoanalytic theories have continued to evolve alongside congitive-behavioural and systemic-family approaches been popular but are now less so. Evolutionary psychology may be used as an overall explanatory theory, and attachment theory is another kind of evolutionary-psychological approach sometimes applied in the context of mental disorders. A distinction is sometimes made between a "medical model" or a "social model" of disorder and disability.
Studies have indicated that genes often play an important role in the development of mental disorders, although the reliable identification of connections between specific genes and specific categories of disorder has proven more difficult. Environmental events surrounding pregnancy and birth have also been implicated. Traumatic brain injury may increase the risk of developing certain mental disorders. There have been some tentative inconsistent links found to certain viral infections,^[13] to substance misuse, and to general physical health.
Abnormal functioning of neurotransmitter systems has been implicated, including serotonin, norepinephrine, dopamine and glutamate systems. Differences have also been found in the size or activity of certain brain regions in some cases. Psychological mechanisms have also been implicated, such as cognitive (e.g. reason), emotional processes, personality, temperament and coping style.
Social influences have been found to be important, including abuse, bullying and other negative or stressful life experiences. The specific risks and pathways to particular disorders are less clear, however. Aspects of the wider community have also been implicated, including employment problems, socioeconomic inequality, lack of social cohesion, problems linked to migration, and features of particular societies and cultures.