Autistic Children (including High-functioning) Have Excessive Serotonin Levels


Nov 26, 2017
Vitamin A improves the symptoms of autism spectrum disorders and decreases 5-hydroxytryptamine (5-HT): A pilot study

•ASD children have lower serum retinol and higher 5-HT levels than control children.

•Autistic children’s symptoms improved and serum 5-HT levels decreased after VAS.

•Compared to baseline, mRNA expression levels of RARα, γ and TpH 1 were changed significantly after VAS.

Autism spectrum disorders (ASD) are complicated neurodevelopmental disorders. Many studies have demonstrated that children with autism have multiple nutritional deficiencies and increased serum 5-hydroxytryptamine (5-HT) levels. In our previous study, 77.9% of autistic children were found to have vitamin A deficiency, and the concentration of vitamin A was negatively associated with the CARS score. In the present study, we sought to test whether vitamin A supplementation could improve autistic symptoms and decrease serum 5-HT levels. The DSM-V criteria and CARS score were used for symptom description and symptom assessment of the patients, respectively, before and after vitamin A supplementation (VAS). Serum retinol and 5-HT levels, mRNA levels of RAR α, β, and γ and TpH 1 expression were detected in autistic children before and after VAS and in normal children. Serum retinol levels in children with ASD were significantly lower than in control children. Serum 5-HT levels in children with ASD were higher than in control children, which were correlated with symptom severity of children with autism. After VA supplementation, the children with ASD exhibited significant improvement in autism symptoms. Serum retinol concentrations of children with ASD were significantly increased, and serum 5-HT levels were decreased. Moreover, statistically significant changes were observed in mRNA expression levels of RAR α, RAR γ and TpH 1 after VAS compared to baseline. This study suggested that VA supplementation may improve symptoms and reduce 5-HT levels in children with ASD, indicating that VA supplementation is a reasonable therapy at least for a subset of children with autism.


Jul 29, 2014
Thanks for posting.

I can't comment on the CARS test they talk about in the study, so I don't know how effective the vitamin A is, but families of the children said they saw improvements, so that is something to consider. The vitamin A supplementation significantly lowered serum 5-HT levels though...


I always enjoy the intro's and discussion portions of studies. Here are some parts I found interesting...

"As a subset of autistic patients have been consistently observed with hyperserotonemia, the serotonergic system is thought to be implicated in ASD etiology. Serotonin is synthesized much more in non-autistic children before 5 years of age than in adults, and the synthesis reduces thereafter. In contrast, serotonin synthesis in children with autism raises continuously until 15years of age to 1.5 times adult levels (Chugani et al., 1999)."

"It was described that approximately one-third of autistic patients exhibited hyperserotonemia, and their blood serotonin level was pertinent to symptoms of self-injury (Kolevzon et al., 2010), making it a potential candidate biomarker for ASD."

"In particular, children with ASD have problems with food selectivity, limited food variety and inadequacy of some food intake, implying risks of nutritional deficiencies (Mari-Bauset et al.,2015). They experience significantly more feeding problems versus their peers, and nutrient analyses revealed significantly lower intake of calcium and protein in ASD patients (Sharp et al., 2013). Reports by Bandini et al. and Hyman et al. demonstrated that nutrients inadequacy (include vitamin A, vitamin D, vitamin E, calcium, etc.) were more common in children with ASD than in typically developing children (Bandini et al., 2010; Hyman et al., 2012). In China, a study by Sunet al. showed that the levels of vitamin A, vitamin B6, Zn and Ca intake were less than 4/5 of the dietary reference intake in children with autism. In addition, compared with normal children, serum Ca, vitamin A and folate levels in autistic children were significantly lower (Sunet al., 2013)."

"Vitamin A was found to be the most seriously deficient nutrient in children with ASD in our earlier study, and a low serum VA level maybe a risk factor for ASD (Liu et al., 2016)."

"Researchers observed that peripheral 5-HTconcentrations were positively correlated with autistic severity (Yanget al., 2015) and negatively correlated with verbal abilities (Hranilovicet al., 2007). A study by Muller also suggested undeniable evidence for the significant function of the serotonin system in social behavior, cognitive flexibility, and sensory development (Muller et al., 2016)."

"We classified patients to mild-moderate ASD and severe ASD according to the CARS scores and compared their serum serotonin levels. The results (Fig. 4) showed that5-HT was significantly higher and retinol was significantly lower in children with severe ASD compared to those with mild-moderate ASD, suggesting that the severity of autistic symptoms is closely related to 5-HT levels and that proper retinol levels may play a role in controling ASD symptoms."


Jun 25, 2017
25(OH)D near the top of the range is said to normalize behaviour. 300 IU/kg D3 for 4 months is an autism treatment. Following, I suppose enough D3 would be taken to maintain serum near 100 ng/dL. On the other hand, they could just stay at 300 IU/kg if taking enough magnesium and vitamin K(2 MK-4; 10 IU : 2 mcg+).

Did vitamin A reduce serotonin in the brain or body? Vitamin D is said to increase it in the brain and lower in the body, the opposite of normal for those with autism.
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