Your body is capable of producing the right neurotransmitters and other regulatory hormones for everything you need, once you set the preconditons for this to occur. The preconditions consist of an efficient digestive system that makes enough bile, digestive enzymes and, yes, serotonin, and a balanced diet and lifestyle (as outlined in my book Timeless Secrets of Health & Rejuvenation, formerly The Key to Health and Rejuvenation, www.ener-chi.com) . The liver plays a key role in the nourishment of the body, and especailly the brain and nervous system. Bile duct blockage in the liver due to accumulation of stones is behind most digestive disorders affecting brain chemistry. They can be removed through a series of liver cleanses and colon cleanses (see my book The Amazing Liver & Gallbladder Flush, www.ener-chi.com). The colon is responsible for absorbing important nutrients for the brain and needs to be clean in order to do so. Sleeping from 10pm is essentail for the nervous system to be balanced and produce balanced amounts of brain chemicals (see Timeless Secrets...)