Physical causes of disease
Physical causes include major brain trauma, accidental head injury, and drug use, such as alcohol and narcotics. Immediate effects have been conclusively traced to these causes.
Historically only two psychiatric disorders have been definitively linked to causes. General paresis of the insane is known to be caused by syphilis and pellagrous insanity is caused by niacin deficiency. Ironically neither of these are any longer thought of as psychiatric disorders.
For disorders such as depression, causation is still controversial. One popular theory is that subtle, possibly hereditary, disturbances in brain chemistry cause depression. The evidence for this view is a statistical correlation between brain chemistry and symptoms. Further evidence is the apparent success of medical treatment (such as the use of Prozac and other selective serotonin re-uptake inhibitors (SSRIs)), which often results in both changes in brain chemistry and alleviation of symptoms. On the other hand, many studies have found that placebos are equally or more effective.
Thomas Laughren, who heads the group of scientists at the FDA that evaluates the medicines, says that "Psychiatric diagnosis is descriptive. We don't really understand psychiatric disorders at a biological level." (source Washington Post)
Many psychiatric diseases might best be considered as syndromes, that is, consistent groups of symptoms that do not always have a single cause.
Non-physical causes of disease
Traditionally various things such as stress upbringing etc have been blamed for causing psychiatric illness. While such things may possibily cause neurotic illness (such as anxiety and minor depression) there is no evidence that there are non physical causes for major psychiatric illnesses such as schizophrenia, bipolar disorder and psychotic depression.
Schizophrenia is regarded as an illness with a susceptibility (probably genetic but in some cases could be due to other things such as a vertically transmitted retrovirus) and an environment cause. The majority of environmental causes are likely to be infections (most likely viruses), although toxins remain a remote possibility in some cases.
The group of psychotic illness are due to brain damage. The timing, severity and position of the brain determine the clinical syndrome. People with mental may or may not have a characteristic pre-illness personality. Those in which genetic features dominate are more likely to have a pre-illness personality profile (such as the autism spectrum) and those predominantly relate to an environental insult such as infection are more likely to have a normal pre-illness personality. Studies have shown characteristic personality traits in schizophrenia patients 1-2 years before a pychosis but "predisposing" traits are not seen when you look at personality earliear say 3 -4 years before first psychosis. This probably reflects the time course of the brain injury. ie damage is occurring during the prodrome to psychosis.
Psychaitric patients do not cope well with stress, but that does not mean stress causes psychiatric illness.
mention emotional stress, bereavement etc.
Physical causes of recovery
mention psychiatric drugs here
Non-physical causes of recovery
Non-physical causes include care and attention from health professionals and others, as well as the patient's belief in the efficacy of the prescribed regimen. To date, the degree of effectiveness of various interventions remains an open question, although the success of placebo treatment furnishes promising clues.
As with most non-psychiatric diseases, some patients will experience spontaneous remissions, in which the condition improves without treatment or any identifiable cause.