Tryptophan is a naturally occurring substance which can be used to improve mood in people who are feeling low or depressed. It is in fact an "amino-acid" and is found in many foods. It is usually used with other antidepressants as tryptophan seems to work better with other drugs than on its own.

The brain has many naturally occurring chemical messengers (or neurotransmitters"). One of these is called serotonin or 5-HT. It is known that lower than normal serotonin (or 5-HT) levels occur in the brain of people who are feeling depressed. Tryptophan is converted into serotonin in the body. If you then take tryptophan tablets this can increase the amount of serotonin in the brain and help to improve your mood.

If too little serotonin (or noradrenaline) produces the symptoms of depression then correcting this should help to reduce the symptoms. There are many ways of doing this e.g. one way of doing this is to block the reuptake (recycling) of transmitters (which is what SSRI antidepressant do). Another way is to increase the amount of serotonin made in the brain cells. Tryptophan is an amino acid and is a precursor of serotonin ie the cells make serotonin (or 5-hydroxy-tryptamine to be pedantic) out of tryptophan. Increasing the amount of tryptophan helps make sure that enough serotonin can be made. By increasing the amount made, the next time an impulse comes along there is more transmitter, a stronger message is passed, and activity in that part of the brain is increased.