Overview
Schizophrenia is most commonly characterised by both 'positive symptoms' (those additional to normal experience and behaviour) and negative symptoms (the lack or decline in normal experience or behaviour). Positive symptoms are grouped under the umbrella term psychosis and typically include delusions, hallucinations, and thought disorder. Negative symptoms may include inappropriate or lack of emotion, poverty of speech, and lack of motivation. Additionally, neurocognitive deficits may be present. These take the form of reduction or impairment in basic psychological functions such as memory, attention, problem solving, and social cognition. The onset is typically in late adolescence and early adulthood, with males tending to show symptoms earlier than females.
Psychiatrist Emil Kraepelin was first to make the distinction between what he called dementia praecox and other forms of madness. This classification was later renamed 'schizophrenia' by psychiatrist Eugene Bleuler as it became clear Kraepelin's name was not an adequate description of the condition.
The diagnostic approach to schizophrenia has been opposed, most notably by the anti-psychiatry movement, who argue that classifying specific thoughts and behaviours as illness allows social control of people that society finds undesirable but who have committed no crime.
More recently, it has been argued that schizophrenia is just one end of a spectrum of experience and behaviour, and everybody in society may have some such experiences in their life. This is known as the 'continuum model of psychosis' or the 'dimensional approach' and is most notably argued for by psychologist Richard Bentall and psychiatrist Jim van Os.
Although no definite causes of schizophrenia have been identified, most researchers and clinicians currently believe that schizophrenia is primarily a disorder of the brain. It is thought that schizophrenia may result from a mixture of genetic disposition (genetic studies using various techniques have shown relatives of people with schizophrenia are more likely to show signs of schizophrenia themselves) and environmental stress (research suggests that stressful life events may precede a schizophrenic episode).
It is also thought that processes in early neurodevelopment are important, particularly those that occur during pregnancy. In adult life, particular importance has been placed upon the function (or malfunction) of dopamine in the mesolimbic pathway in the brain. This theory, known as the dopamine hypothesis of schizophrenia largely resulted from the accidental finding that a drug group which blocks dopamine function, known as the phenothiaziness, reduced psychotic symptoms. These drugs have now been developed further and antipsychotic medication is commonly used as a first line treatment. However, this theory is now thought to be overly simplistic as a complete explanation.
History
Accounts that may relate to symptoms of schizophrenia date back as far
as 2000 BC in Book of Hearts, a part of the ancient Ebers papyrus. However, a recent study1 into the ancient Greek and Roman literature showed that whilst the general population probably had an awareness of psychotic disorders, there was no condition that would meet the modern diagnostic criteria for schizophrenia in these societies.
This nonspecific concept of madness has been around for many thousands of years and schizophrenia was only classified as a distinct mental disorder by Kraepelin in 1887. He was the first to make a distinction in the psychotic disorders between what he called dementia praecox (a term first used by psychiatrist Benedict A. Morel) and manic depression. Kraepelin believed that dementia praecox was primarily a disease of the brain2, and particularly a form of dementia. Kraepelin named the disorder 'dementia praecox' (early dementia) to distinguish it from other forms of dementia (such as Alzheimer's disease) which typically occur late in life. He used this term because his studies focused on young adults with dementia.22
The term schizophrenia is derived from the Greek words 'schizo' (split) and 'phrene' (mind) and was coined by Eugene Bleuler to refer to the lack of interaction between thought processes and perception. He was also the first to describe the symptoms as "positive" or "negative."22 Bleuler changed the name to schizophrenia as it was obvious that Krapelin's name was misleading. The word "praecox" implied precocious or early onset, hence premature dementia, as opposed to senile dementia from old age. Bleuler realised the illness was not a dementia (it did not always lead to mental deterioration) and could sometimes occur late as well as early in life and was therefore misnamed.
With the name 'schizophrenia' Bleuler intended the name to capture the separation of function between personality, thinking, memory, and perception, however it is commonly misunderstood to mean that affected persons have a 'split personality' (something akin to the character in Robert Louis Stevenson's The Strange Case of Dr. Jekyll and Mr. Hyde). Schizophrenia is commonly, although incorrectly, confused with multiple personality disorder (now called 'dissociative identity disorder'). Although people diagnosed with schizophrenia may 'hear voices' and may experience the voices as distinct personalities, schizophrenia does not involve a person changing between distinct multiple personalities. The confusion perhaps arises in part due to the meaning of Blueler's term 'schizophrenia' (literaly 'split mind'). Interestingly, the first known misuse of this word schizophrenia to mean 'split personality' (in the Jekyll and Hyde sense) was in an article by the poet T. S. Eliot in 19333.
In the first half of the twentieth century, schizophrenia was considered by many as a "hereditary defect," and schizophrenics became the target of the eugenics programs of many countries. Tens of thousands were forcibly sterilized, the majority in Germany, the United States, and various Scandinavian countries.
Diagnosis and presentation (signs and symptoms)
Like many mental illnesses, the diagnosis of schizophrenia is based upon the behaviour of the person being assessed. There is a list of diagnostic criteria which must be met for a person to be so diagnosed. These depend on both the presence and duration of certain signs and symptoms.
The most commonly-used criteria for diagnosing schizophrenia are from the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM) and the World Health Organisation's International Statistical Classification of Diseases and Related Health Problems (ICD). The most recent versions are ICD-10 and DSM-IV-TR.
Below is an abbreviated version of the diagnostic criteria from the DSM-IV-TR, the full version is available here.
To be diagnosed as having schizophrenia, a person must display:
- A) Characteristic symptoms: Two or more of the following, each present for a significant portion of time during a one-month period (or less, if successfully treated)
- delusions
- hallucinations
- disorganized speech (e.g., frequent derailment or incoherence). See thought disorder.
- grossly disorganized or catatonic behavior
- negative symptoms, i.e., affective flattening (lack or decline in emotional response), alogia (lack or decline in speech), or avolition (lack or decline in motivation).
Note: Only one Criterion A symptom is required if delusions are bizarre or hallucinations consist of hearing voices.
- B) Social/occupational dysfunction: For a significant portion of the time since the onset of the disturbance, one or more major areas of functioning such as work, interpersonal relations, or self-care, are markedly below the level achieved prior to the onset.
- C) Duration: Continuous signs of the disturbance persist for at least six months. This six-month period must include at least one month of symptoms (or less, if successfully treated) that meet Criterion A.
Historically, schizophrenia in the West was classified into simple, catatonic, hebephrenic, and paranoid. The DSM now contains five sub-classifications of schizophrenia. These are
- catatonic type (where marked absences or peculiarities of movement are present),
- disorganised type (where thought disorder and flat or inappropriate affect are present together),
- paranoid type (where delusions and hallucinations are present but thought disorder, disorganised behaviour, and affective flattening is absent),
- residual type (where positive symptoms are present at a low intensity only) and
- undifferentiated type (psychotic symptoms are present but the criteria for paranoid, disorganized, or catatonic types has not been met).
Symptoms may also be described as 'positive symptoms' (those additional to normal experience and behaviour) and negative symptoms (the lack or decline in normal experience or behaviour). 'Positive symptoms' describe 
