Classification of schizophrenia. Schizophrenia is classified as a severe mental disorder characterised by a range of symptoms. Positive symptoms include hallucinations, such as hearing voices, and delusions, which are false, fixed beliefs. Negative symptoms include speech poverty, where communication becomes limited, and avolition, marked by a lack of motivation or goal-directed behaviour

The dopamine hypothesis of schizophrenia has evolved from its original form, which linked dopamine overactivity in the mesolimbic system to positive symptoms, to the reformulated dopamine hypothesis, which also recognises dopamine underactivity in the mesocortical pathway as a cause of negative symptoms. Further research into neural correlates has identified glutamate dysregulation, where reduced glutamate activity may contribute to cognitive and emotional deficits. These insights highlight schizophrenia as a disorder involving a complex interplay of neurotransmitters beyond just dopamine.