Serotonin or 5-hydroxytryptamine (5-HT), is a neurotransmitter that has been considered to be involved in schizophrenia, because the hallucinogen lysergic acid diethylamide (LSD) is a 5-HT2 receptor agonist which resulted in psychosis like symptoms.



Several receptor subtypes of 5-HT have been identified to contribute to the symptoms of schizophrenia. It has become apparent that antagonism of 5-HT2A receptors contributes to the activity of some of the newer antipsychotic drugs such as clozapine and risperidone. There is also compelling evidence for the association between allelic variation of 5-HT2A receptors and schizophrenia.

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Finally, post-mortem and imaging studies have supported the role of 5-HT in causing schizophrenia and have shown a reduced expression of 5-HT2A receptors in the frontal cortex in schizophrenia.