This paper examines the relationship between schizophrenia, suicide, serotonin, and insulin. The author describes how brain insulin regulates catecholamine and serotonin activity. If serotonin levels are impaired the regulation of insulin release will be compromised, leading to further negative effects on serotonin. Chronic stress down-regulates serotonin and induces insulin resistance which, induces persistent hyperglycaemia, which is responsible for an array of psychiatric disturbances.