Major depression, bipolar syndromes, and schizophrenia

Psychiatry is a medical subspecialty dealing with mental and behavioral disorders. Mental illness refers to diseases of the brain, because the mind is a function of the brain, and illness is a synonym for disease. Psychiatric illnesses are generally differentiated from neurological illnesses in that neurological disorders tend to have demonstrable anatomical or physiological abnormalities associated with them. Although the biological basis of psychiatric disorders is well established, the neurochemical and neuroanatomical abnormalities associated with these disorders tend to be subtle. Recent advances in brain imaging and molecular genetics provide optimism regarding our ability to understand psychiatric illnesses on a more biological and molecular basis. However, at this time, psychiatric diagnoses remain clinical and descriptive. That is to say, they are based on observation regarding symptoms, complications, and outcome. The basis of psychiatric diagnosis continues to be the psychiatric interview and mental status examination. At this time, there are no laboratory or imaging tests to diagnose mental illnesses, though laboratory tests may be helpful in diagnosing medical conditions with psychiatric symptoms, such as thyroid disease.