Historical and Contemporary Understandings
Mental illness was not well understood in ancient times. Conditions like schizophrenia were not differentiated from other forms of mental illness or mental retardation, much of which was thought of as being supernatural in origin, caused by evil spirits, demon possession, punishment for sin, or similar spiritualist phenomena. Apart from exorcism, an early remedy for such conditions was found in trepanation, a surgical procedure in which holes were drilled in the skull, perhaps as a means of letting those evil spirits out, perhaps for other, unknown reasons. Though the practice of trepanation was ultimately discontinued in developed cultures, the idea that schizophrenia was essentially a spiritual and moral problem appears to have remained dominant for hundreds, if not thousands of years.
The first, formal description of schizophrenia as a mental illness was made in 1887 by Dr. Emile Kraepelin. He used the term "dementia praecox" to describe the symptoms now known as schizophrenia. Dementia praecox means "early dementia". By calling his syndrome 'early dementia', he meant to differentiate it from dementias that occur later in life such as Alzheimer's disease (senility). Correctly, Kraepelin believed that dementia praecox was primarily a disease of the brain. However, he was mistaken in believing that this disorder was a form of dementia. It is now known that schizophrenia and dementia (mental deterioration) are distinct disorders.
The term "schizophrenia" was first used in 1911 by a Swiss psychiatrist, Eugen Bleuler. It comes from the Greek roots schizo (split) and phrene (mind). Bleuler used this name to emphasize the mental confusion and fragmented thinking characteristic of people with the illness. His term was not meant to convey the idea of an actual split or multiple personality. This confusion has, however, become a common and rather entrenched myth regarding schizophrenia that continues to this day.
Although Bleuler was the first to describe symptoms as "positive" or "negative", both Kraepelin and Bleuler recognized that schizophrenia symptoms tended to cluster into distinct categories. They created a typology of schizophrenic subtypes that continues to be used today. Modern schizophrenic categories recognized by the DSM (Diagnostic and Statistical Manual of Mental Disorders; the repository of mental health diagnoses, currently in its fourth, text-revised edition) include paranoid, disorganized, catatonic, residual, and undifferentiated subtypes, each based on a particular distinct symptom cluster.
The next major contribution to the progress of understanding schizophrenia came when Kurt Schneider listed his 'first rank' features of the disease in 1959. This important work effectively differentiated schizophrenia from other psychoses and served as the inspiration for the two diagnostic manuals widely used to define modern schizophrenia, the International Classification of Diseases (ICD, currently in its 10th edition) and the DSM. The definition and diagnostic criteria for schizophrenia codified in these manuals continue to evolve today, based primarily on new research findings that further illuminate the illness.
As the classification of schizophrenia became more refined, so too did the theories of how it was caused. Gregory Bateson and colleagues offered the "double bind" theory in the middle 1950's. This theory proposed that schizophrenia was caused by particular forms of bad parenting, specifically where parents explicitly said one thing and then contradicted that thing with implicit unconscious messages of opposite content. For example, parents might praise their child, but treat him poorly. This theory has been largely discredited and discarded for lack of convincing scientific evidence. However, the idea that stressful life events (such as having crazy parents) can play a role in causing schizophrenia continues to be important in modern "diathesis-stress" models of schizophrenia.
A diathesis is a vulnerability. Diathesis-stress models of schizophrenia basically propose that people have predispositions and vulnerabilities for schizophrenia (diatheses). Some people have more of these susceptibilities than others, for varying reasons having to do with genetics, biology and experience. However, propensity towards schizophrenia alone is not enough to trigger the disorder. Instead, people's vulnerabilities must interact with life stresses to trigger the onset of the illness. The greater a person's inherent propensity for developing schizophrenia, the less stress is necessary to trigger a psychotic episode and get the disorder started. Conversely, where there is a smaller susceptibility for developing schizophrenia, a greater stress is required to produce the disorder. Until this critical amount of stress is reached (however much or little of it is necessary) people cannot be said to have schizophrenia, and their vulnerabilities might be said to be "latent" (hidden). Various sources of stress may combine to produce the releasing effect, including stressors which are psychological, social, and biological (including trauma, depression, viruses, birth complications, and similar illnesses). The use of certain 'recreational' drugs such as marijuana or LSD may also be capable of releasing a hidden diathesis towards developing schizophrenia.