Many different professions may be involved in studying mental disorders or distress. Most notably, psychiatrists and clinical psychologists are particularly interested in this area and may either be involved in clinical treatment of mental illness, or research into the origin, development and manifestations of such states, or often, both.
More widely, psychopathology may be involved in many different specialties. For example, a neuroscientist may focus on brain changes related to mental illness. Therefore, someone who is referred to as a psychopathologist, may be one of any number of professions who have specialized in studying this area.
Psychiatrists in particular are interested in descriptive psychopathology, which has the aim of describing the symptoms and syndromes of mental illness. This is both for the diagnosis of individual patients (to see whether the patient's experience fits any pre-existing classification), or for the creation of diagnostic systems (such as the Diagnostic and Statistical Manual of Mental Disorders or International Statistical Classification of Diseases and Related Health Problems) which define which signs and symptoms should make up a diagnosis, and how experiences and behaviours should be grouped in particular diagnoses (e.g. clinical depression, paraphrenia, paranoia, schizophrenia).
Before diagnosing a psychological disorder, Clinicians must study the themes, also known as abnormalities, within psychological disorders. The most prominent themes consist of: deviance, distress, dysfunction and danger. These themes are known as the 4 D's, which define abnormality