Serotonin is a neurotransmitter in the brain that is largely responsible for mood, learning, language, and sensory integration among many things. It is also used in early development to differentiate neuronal networks in the brain. 5-hydroxytryptophan, or 5-HTP, is a precursor to serotonin that is commonly taken orally for sleep and anxiety. Croonenberghs J, et al. proved that autistic subjects had higher levels of serotonin when given 5HTP compared to controls, all subjects were 13-19 years and male. This is possibly due to more serotonin synthesis in the intestines and genetic changes in vitamin B6 metabolism. (1)

Individuals with ASD are known to have altered diurnal rhythms (see Melatonin) as well as cortisol levels, the stress hormone. Cortisol is naturally high in the morning and slowly declines towards the evening. However, those on the spectrum have a backwards relationship with higher levels before bed, making it harder to sleep as well. They also have higher cortisol spikes in novel situations compared to controls, and greater sensory sensitivity because of this. (2)

Cortisol which is too high can be neurotoxic, potentially propagating the cell danger response. (1) 5-HTP is a nutritional workaround to help increase melatonin, decrease cortisol, decrease glutamate, therefore lowering neuron excitotoxicity.

  • Croonenberghs J, et al. Serotonergic disturbances in autistic disorder: L-5-hydroxytryptophan administration to autistic youngsters increases the blood concentrations of serotonin in patients but not in controls. Life Sci. 2005 Mar 25;76(19):2171-83.

Corbett BA, Schupp CW, Levine S, Mendoza S. Comparing Cortisol, Stress and Sensory Sensitivity in Children with Autism. Autism research : official journal of the International Society for Autism Research. 2009;2(1):39-49. doi:10.1002/aur.64.