Psychiatry involves theories of the mind, theories of the causes of mental disorders, classification schemes for those disorders, research about the disorders, proven treatments and research into new treatments, and a number of professions whose job it is to work with or on behalf of people with mental disorders. The philosophical study of psychiatry discusses conceptual, ethical, metaphysical, social, and epistemological issues that arise in all these aspects of psychiatry. Central to this study is the nature of mental illness.

The central philosophical debate over mental illness is not about its existence, but rather over how to define it, and whether it can be given a scientific or objective definition, or whether normative and subjective elements are essential to our concept of mental illness. One desideratum for a successful definition of mental illness is that it will settle debates over particular purported mental illnesses.

The connection between philosophical issues in the study and treatment of mental illness and these other areas of philosophy is in many cases obvious, as in the question of when and how people with mental disorders are responsible for their actions is connected with the insanity defense in law, and the more general debate over the justification of punishment. The philosophical investigation of the nature of mental illness is therefore relevant to many other areas of philosophy. While there is no sharp divide between the philosophical discussion of the nature of mental illness and the wider philosophical discussion of psychiatry, we can focus on four major issues that have preoccupied the philosophical literature.

What Causes Mental Illness?
Although the exact cause of most mental illnesses is not known, it is becoming clear through research that many of these conditions are caused by a combination of genetic, biological, psychological and environmental factors. One thing is for sure—mental illness is not the result of personal weakness or a character defect, and recovery from a mental illness is not simply a matter of will and self-discipline.

Heredity (genetics): Many mental illnesses run in families, suggesting that the illnesses may be passed on from parents to children through genes. Genes contain instructions for the function of each cell in the body and are responsible for how we look, act, think, etc.

Biology:Some mental illnesses have been linked to an abnormal balance of special chemicals in the brain called neurotransmitters. Neurotransmitters help nerve cells in the brain communicate with each other. If these chemicals are out of balance or are not working properly, messages may not make it through the brain correctly, leading to symptoms of mental illness. In addition, defects in or injury to certain areas of the brain also have been linked to some mental conditions.

Psychological trauma: Some mental illnesses may be triggered by psychological trauma suffered as a child, such as severe emotional, physical or sexual abuse; a significant early loss, such as the loss of a parent; and neglect.