Serotonin is a vital hormone in the normal functioning of the central nervous system. This neurotransmitter is a key regulator of various bodily functions including sleep, mood, appetite, intestinal movement, feeding and body weight.

Serotonin is also thought to play a role in some mental health disorders that may lead to problems such as suicidal tendencies, obsessive compulsive disorder, alcoholism, and anxiety. Some of the disorders that are thought to be related to the biosynthesis and availability of serotonin include:

• Sudden infant death syndrome (SIDS) - Studies have shown that defective serotonin signalling in the brain could be responsible for sudden infant death.
• Depression - Low levels of serotonin have been linked to clinical depression. Drugs that raise levels of serotonin in the synaptic cleft such as SSRIs (selective serotonin reuptake inhibitors) have been shown to improve symptoms of depression. Examples of these agents include fluoxetine, fluvoxamine, and citalopram.
• Obsessive compulsive disorder - This describes a condition where a person has compulsive urges to carry out actions that might prevent something they are worried about becoming a reality. For example, they may repeatedly check doors or windows are locked because they are so worried about being burgled. SSRIs have also been successfully in the treatment of OCD.
• Serotonin syndrome - This is a condition characterized by excessively high levels of serotonin, as an adverse effect of serotonergic therapy. This can be life threatening and lead to a severe rise in blood pressure. The syndrome usually occurs as a result of excessive activation of the serotonin receptors and some experts prefer the condition to be called serotonin toxicity or poisoning.