It is rare for one to see an empirical article in a moderately-impactful journal, such as SLEEP, that solely reports about one case study (let alone have multiple affiliations……). I can overlook the extremely small sample size, however, because this study may help my lab elucidate a reciprocal relationship between sleep/wake and reward centers of the brain and related serotonergic and dopaminergic neurosystems.

In this report, a patient with significantly depleted levels of circulating serotonin and dopamine in the brain, which was facilitated by a genetic deficiency in sepiapterin reductase (an enzyme necessary for the synthesis of the amino acids responsible for making serotonin and dopamine (tryptophan and tyrosine), suffered from multiple physiological and subsequent behavioral ailments, including hypersomnia (over-sleeping), hyperphagia (over-eating), impaired cognition/attention, depressed melatonin secretion, and ultradian sleep/wake rhythms (more than one sleep/wake rhythm in a 24 hour period (day)). Following treatment with 5-hydroxytryptophan, which is a serotonin/melatonin precursor, the patient’s sleep/wake rhythms became more consolidated, over-eating decreased, melatonin profiles were normalized, and serotonin levels rose. Of all the rescuing effects of 5-hydroxytryptophan, it is most fascinating that over-eating, a behavior clearly indicative of altered dopaminergic/other neurosystems in reward areas, was mitigated. For addicts (independent of type: drugs, sex, food, gambling, etc), 5-hydroxytryptophan may not only reduce craving, but may also effectively reduce relapse risk, since assiduous disruptions of sleep/wake predict relapse risk.

This picture, adopted from the paper, shows the overlapping biochemical pathways leading to serotonin, dopamine, and melatonin synthesis.
ResearchBlogging.org

Smaranda Leu-Semenescu; Isabelle Arnulf; Caroline Decaix; Fathi Moussa; Fabienne Clot; Camille Boniol; Yvan Touitou; Richard Levy; Marie Vidailhet; Emmanuel Roze (2010). Sleep and Rhythm Consequences of a Genetically Induced Loss of Serotonin SLEEP, 33 (3), 307-314