Neurotransmitters and Mental Health: Neurotransmitters play a significant role in mental health. For example serotonin regulates mood, sleep and appetite. Too little serotonin has been found in people suffering from depression. Some antidepressants medications work by increasing the availability of serotonin at postsynaptic receptor sites. High levels of the neurotransmitter dopamine have been associated with symptoms of schizophrenia. Drugs that block dopamine activity have been found to reduce symptoms of schizophrenia.