Schizophrenia

File:Schizophrenia.jpg

This painting embodies the bizarre and distorted experience of individuals who suffer from schizophrenia.

Schizophrenia is a mental disorder characterized by patterns of disordered thought, language, motor, and social function. During the acute stage of schizophrenia, individuals experience a break from reality although this does not mean they have multiple personalities. Despite popular perception, dissociative identity disorder (formerly known as multiple personality disorder) and schizophrenia are completely separate disorders.

The cause of schizophrenia is unknown, although several neurotransmitters and brain structures are hypothesized to play a role in this disorder and are considered in Causes section.

Diagnosis and classification

Note: The American Psychiatric Association, which publishes the Diagnostic and Statistical Manual of Mental Disorders, forbids the unauthorized reproduction of their diagnostic criteria. A narrative of the DSM-IV-TR criteria follows. For a person to be diagnosed with schizophrenia, a person must display two or more of the following symptoms for a significant portion of one-month, and must cause a significant level of disturbance in one's life: delusions, hallucinations (usually auditory as visual are rare), disorganized speech, disorganized speech, or negative symptoms. (These symptoms are classified as criterion A in the DSM).

However, only one of these symptoms is required if the delusions are bizarre, the patient hallucinates an auditory commentary of their actions or hears two or more voices participating in conversation with each other. Signs must be persist for at least six months since the onset of the disturbances, with at least one month of symptoms that meet the first outlined criteria, and may be during the prodromal or residual periods. The symptoms of these periods may manifest as only negative symptoms, or by two or more of the criterion A symptoms.

As with any disorder, there several criteria that exclude a diagnosis. A patient will not receive a diagnosis of schizophrenia if they are schizoaffective or have a mood disorder with psychotic features, as no mood disorders occur at the same time as active phase symptoms, or have a brief duration compared to the active and residual phases. Substance use and medical conditions can mimic schizophrenia, and so a diagnosis will not be made if symptoms are due to their direct effects. A history of autism or another pervasive developmental disorder will exclude a diagnosis of schizophrenia unless prominent delusions or hallucinations are present for more than a month.

Subtypes

There are several general patterns of schizophrenia. These subtypes have been identified to aid research, treatment, and communication. Each pattern is not always as distinct as is presented below

Disorganized schizophrenia is prominent disorganized speech and behavior, with flat or inappropriate affect (display of emotion). This subtype is the closest form of the stereotypical idea of a "crazy person". A patient will not receive this clsasification if they meet the criteria for the catatonic type.

Catatonic schizophrenia is characterized by at least two of the following symptoms: catalepsy (a lack of voluntary movement), excessive and purposeless motor activity (uninfluenced by external stimuli), very strong negativism (maintaing a rigid position and resists all attempts to be moved) or mutism, peculiar voluntary movement and posturing (often taking bizarre or inappropriate positions), stereotyped movements, with conspicuous mannerisms or grimacing, or echolalia or echopraxis (immediate repetition of words or actions of others).

Paranoid schizophrenia is characterized by delusions or hallucinations of a relatively consistent nature, usually related to themes of persecution or grandeur. Positive symptoms are most prominent as the patient retains largely coherent speech, a fairly normal display of emotions behavior. The prognosis is favorable, as it responds well to antipsychotic medication.

Undifferentiated schizophrenia occurs when the symptoms meet criterion A, and the patient does not fit into the paranoid, disorganized, or catatonic subtypes.

Residual schizophrenia has the absence of prominent delusions and hallucinations, disorganized speech or catatonic behaviour. However, there is a continued disturbance as marked by having two or more criterion A symptoms, but present in a weakened form. These symptoms could take the form of odd beliefs, or unusual (but not psychotic) perceptual experiences.

Dimensions

Another way of classifying schizophrenic behaviors is by identifying symptoms that exist on a continuum with varying degrees of severity rather than discrete groups.,

The positive-negative dimension comprises positive symptoms, meaning the presence of something normally absent, characterized by prominent delusions, hallucinations, positive formal thought disorder, and persistently bizarre behavior. Negative symptoms are the absence of something that is normall present, such as flattened or masked affect, alogia, avolition, anhedonia, and attentional impairment. The Positive and Negative Syndrome Scale (PANSS) is a 30-item psychiatric rating scale that can gauge the relationship of positive and negative symptoms, their differential, and the severity of illness.

The paranoid-nonparanoid dimension is the presence or absence of delusion of persecution or grandeur. This dimension may be related to the process-reactive dimension.

The process-reactive, or good-poor premorbid dimension attempts to classify the variation in acute symptom onset. Some individuals experience a prolonged prodromal phase, while others go from normal functioning to full-blown psychosis within days. Cases with a gradual onset are called process, while sudden onset precipitated by a traumatic or stressful event is called reactive. A more continuous dimension is the good-poor dimension that describes how well the patient functioned before the active phase onset. These adjustment are useful in predicting prognosis as individuals with poor-premorbid schizophrenia are more likely to have long hospitalizations, and more likely to require re-hospitalization compared with good-premorbid patients.

Type I and Type II.

Course of illness

Individuals differ in symptom intensity and presentation over time. Schizophrenia is considered a chronic, relapsing disorders since patients will experience residual symptoms after an active period, and cycle between the two.

Prodromal

The prodromal phase is a gradual deterioration of functioning, marked by strange behaviour and social isolation. This is before any clear psychotic symptoms appear, and may last for years or days before developing into full blown, active schizophrenia.

Active

The active phase is marked by prominent psychotic symptoms.

Residual

The residual phase occurs after an active period, and individuals will continue to experiences cognitive, behavioral, and social dysfunctions but not as strongly as during a psychotic episode.

Causes

The exact cause of schizophrenia is unknown, but several biochemical and structural abnormalities have been found and remain the focus for research and treatment. Antipsychotic medication may produce cognitive deficits, so researchers are challenged to differentiate between the illness and drug side-effects, as well as co-morbid mental disorders and illicit drug use.

The dopamine hypothesis of schizophrenia, that is, schizophrenia may be due to a dopaminergic dysregulation, is based on several lines of evidence. First, individuals with Parkinson's disease are treated with dopamine precursors, most commonly L-dopa, which allow the brain to synthesize additional dopamine. Some patients begin to display similar to schizophrenia as a side-effect to the drug, which presumably produce abnormally high levels of dopamine. Also, antipsychotic drugs can produce Parkinsonian side effects by lowering dopamine function. Secondly, amphetamines can induce temporary psychosis and behaviors similar to schizophrenia in otherwise healthy individuals, and it also worsens symptom severity in patients with schizophrenia.

A serendipitous discovery occurred in the 1950s when physicians found that chlorpromazine, a drug used previously for a different purpose, reduced the positive symptoms of schizophrenia. Chlorpromazine is a member of the phenothiazine class of drugs used to treat schizophrenia, and exerts its action by blocking dopamine receptors, thus reducing the effects of dopamine.

This evidence may reflect abnormalities not with dopamine itself, but rather with the systems with which it interacts: the the fronto-striato-pallido-thalamic loops, and the limbic structures, such as amygdala and hippocampus.

Positron emission topography studies have found a loss of grey matter starting in the parietal lobe, and spreading outwards as the disorder progresses. Other neuro-imaging studies have found decreased neuron activity in the dorsolateral prefrontal cortex, which may explain the cognitive deficits in attention and planning.