Any illness with a psychological origin, manifested either in symptoms of emotional distress or in abnormal behaviour. Most mental disorders can be broadly classified as either psychoses or neuroses (see neurosis; psychosis). Psychoses (e.g., schizophrenia and bipolar disorder) are major mental illnesses characterized by severe symptoms such as delusions, hallucinations, and an inability to evaluate reality in an objective manner. Neuroses are less severe and more treatable illnesses, including depression, anxiety, and paranoia as well as obsessive-compulsive disorders and post-traumatic stress disorders. Some mental disorders, such as Alzheimer disease, are clearly caused by organic disease of the brain, but the causes of most others are either unknown or not yet verified. Schizophrenia appears to be partly caused by inherited genetic factors. Some mood disorders, such as mania and depression, may be caused by imbalances of certain neurotransmitters in the brain; they are treatable by drugs that act to correct these imbalances (see psychopharmacology). Neuroses often appear to be caused by psychological factors such as emotional deprivation, frustration, or abuse during childhood, and they may be treated through psychotherapy. Certain neuroses, particularly the anxiety disorders known as phobias, may represent maladaptive responses built up into the human equivalent of conditioned reflexes.
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The Myth of Mental Illness: Foundations of a Theory of Personal Conduct is a controversial book by Thomas Szasz. It is highly influential in the anti-psychiatry movement. In it, Szasz argues that mental illness is a social construct created by doctors, and the term can only be used as a metaphor given that an illness must be an objectively demonstrable biological pathology, whereas psychiatric disorders meet none of these criteria. What psychiatrists label mental illness is in fact nothing more than a deviation from the consensus reality or common morality, Szasz says.
He states that mental illness, madness and even many crimes are created or defined by cultural controls, morals and "real world" views of big science, religion and government, similar to heretics, pagans, and sinners before the industrial revolution. In parts he agrees with Wilhelm Reich, Alexander Lowen, R.D. Laing, Arthur Janov and Peter Breggin. All are psychiatrists, except Janov, who is a psychologist. Their views, theories and psychotherapies are opposed to and rejected by most MD and counselors in the 20th century. Szasz asserts that a positive, present and honest relationship is the basis of his therapy.
The book extends the arguments of Szasz's paper "The Myth of Mental Illness", first published in 1960. In it, Szasz argues that beliefs cannot be caused by brain disease, although such artifacts as visual (or hearing) defects can.