Schizophrenia is a chronic, severe, and disabling brain disorder, clinically manifesting in acute episodes associated with hallucinations, delusions, and disordered thinking and behavior. Signs and symptoms of schizophrenia are divided into three categories: positive symptoms that include psychotic symptoms, negative symptoms that include a decrease in emotional range, poverty of speech, and loss of interests and drive, and cognitive symptoms that include neurocognitive deficits. Schizophrenia affects approximately 0.7% of world populations.
Diagnosis of schizophrenia is based on evaluation by a psychiatrist, tests, and medical history. Schizophrenia requires lifelong treatment with a focus on eliminating the symptoms of the disease, and include antipsychotic medications and various psychosocial treatments.
The cause of schizophrenia is still unknown, but researchers believe that a combination of genetics and environment contributes to development of the disease. Studies show that schizophrenia has a heritability of about 80%. However, it is difficult to relate gene changes to discrete physiological or biochemical changes associated with the disease. The most implicated genes in schizophrenia are those involved in dopamine or glutamate signaling, the two signaling systems. Single nucleotide polymorphisms (SNPs) in the CHL1 gene have been linked to schizophrenia in some populations.