Schizophrenia is one of several psychotic disorders described in the DSM. People with psychotic disorders lose contact with reality and often have delusions or hallucinations. People with schizophrenia have a wide range of symptoms, which can be classified into positive or negative symptoms.
Positive symptoms involve the presence of altered behaviors. Examples of positive symptoms include delusions, hallucinations, disorganized speech, and disorganized behavior. Delusions are false beliefs that are strongly held despite contradictory evidence. Hallucinations are sensory or perceptual experiences that happen without any external stimulus. Hallucinations can occur in any sensory modality, but auditory hallucinations are most common in schizophrenia. Disorganized speech can also take many forms. For example, a person with schizophrenia may produce word salad, which consists of words and sentences strung together in an incoherent way. Examples of disorganized behavior include inappropriate gestures or laughter, agitated pacing, or unpredictable violence.
Negative symptoms involve an absence or reduction of normal behavior. Negative symptoms include emotional flatness, social withdrawal, spare or uninflected speech, and lack of motivation.
Schizophrenia is classified into four subtypes, depending on the symptoms present at the time of evaluation:
As with other psychological disorders, researchers have studied the etiology of schizophrenia from different perspectives.
Research suggests that genes, neurotransmitters, and brain abnormalities play a role in the onset of schizophrenia: