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Serotonin Imbalance in Autism


Autism is a very intricate disorder, and should not be sized down to one single cause or contributing factor. However, one area of imbalance that should be considered is serotonergic activity.

SSRIs and Autism

Recent literature demonstrates that SSRI use during pregnancy can increase the likelihood of offspring having autistic symptoms. One study showed decreased spatial memory and learning in the offspring of rats that were injected with a SSRI in comparison to healthy controls [1]. Additionally, a recent study out of Quebec made headlines in 2015 because of the increased risk SSRIs put on pregnant women. The authors of this article found taking a SSRI during pregnancy can increase the risk of a child developing autism [2]. It can be postulated that this prenatal exposure to SSRIs has a negative genetic effect on children.

The Role of Serotonin

Serotonin dysfunction is likely involved in autism, but what is happening inside the body and brain of an autistic child? Evidence has shown that one area of dysfunction involves the serotonin transporter, SERT. A SERT gene variation called Ala56 has been linked to those on the autistic spectrum. When researchers generated rats with this genetic mutation, they discovered that these rats had an increased rate of serotonin clearance in the hippocampus compared to controls (P<0.0001) [3]. This suggests that SERT activity is upregulated in those with autism, and may explain why SSRI therapy has sometimes been found to be beneficial for decreasing autistic symptoms [4].

In addition to altered SERT activity, elevated serum and urine levels of serotonin have been found in patients with autism [5] [6]. As there is a positive correlation between urinary serotonin levels and cerebrospinal fluid serotonin levels, one may hypothesize that serotonin in autistic individuals is also elevated in the central nervous system [7]. This excess serotonin may be derived from increased serotonin synthesis, as those with autism usually have low levels of l-tryptophan [8]. Therefore, it may be beneficial to assess neurotransmitter levels in those with autism in order to help identify areas of imbalance and potentially aid in the rebalancing of neurotransmitters.

Additionally, it should be noted that doctors need to use extreme caution when deciding whether or not to put pregnant women on SSRIs. Another potential form of therapy that may have fewer negative effects on unborn children may be 5-HTP, which is the biochemical precursor to serotonin. However, safety and efficacy studies are warranted to support this notion. Ask your doctor today about Sanesco’s neurotransmitter assessment for your loved one with autism. For pregnant women, always consult your doctor before taking any supplements or medications.



1.    Sprowles, J. L., Hufgard, J. R., Gutierrez, A., Bailey, R. A., Jablonski, S. A., Williams, M. T., & Vorhees, C. V. (2016). Perinatal exposure to the selective serotonin reuptake inhibitor citalopram alters spatial learning and memory, anxiety, depression, and startle in Sprague-Dawley rats [Abstract]. International Journal of Developmental Neuroscience, 54, 39-52. doi:10.1016/j.ijdevneu.2016.08.007

2.    Boukhris, T., Sheehy, O., Mottron, L., & Bérard, A. (2016). Antidepressant Use During Pregnancy and the Risk of Autism Spectrum Disorder in Children [Abstract]. JAMA Pediatrics JAMA Pediatr, 170(2), 117. doi:10.1001/jamapediatrics.2015.3356

3.    Veenstra-Vanderweele, J., Muller, C. L., Iwamoto, H., Sauer, J. E., Owens, W. A., Shah, C. R., . . . Blakely, R. D. (2012). Autism gene variant causes hyperserotonemia, serotonin receptor hypersensitivity, social impairment and repetitive behavior. Proceedings of the National Academy of Sciences, 109(14), 5469-5474. doi:10.1073/pnas.1112345109

4.    Kolevzon, A., Mathewson, K. A., & Hollander, E. (2006, March 15). Selective Serotonin Reuptake Inhibitors in Autism [Abstract]. The Journal of Clinical Psychiatry, 67(03), 407-414. doi:10.4088/jcp.v67n0311

5.    Naffah-Mazzacoratti M. G., Rosenberg R., Fernandes M. J., Draque C. M., Silvestrini W., Calderazzo L., et al. (1993). Serum serotonin levels of normal and autistic children [Abstract]. Braz. J. Med. Biol. Res. 26 309–317

6.    Mulder, E. J., Anderson, G. M., Kemperman, R. F., Oosterloo-Duinkerken, A., Minderaa, R. B., & Kema, I. P. (2010). Urinary Excretion of 5-Hydroxyindoleacetic Acid, Serotonin and 6-Sulphatoxymelatonin in Normoserotonemic and Hyperserotonemic Autistic Individuals [Abstract]. Neuropsychobiology, 61(1), 27-32. doi:10.1159/000258640

7.    Audhya, T., Adams, J. B., & Johansen, L. (2012). Correlation of serotonin levels in CSF, platelets, plasma, and urine. Biochimica Et Biophysica Acta (BBA) – General Subjects, 1820(10), 1496-1501. doi:10.1016/j.bbagen.2012.05.012

8.     Kałuzna-Czaplinska J, Michalska M, Rynkowski J. Determination of tryptophan in urine of autistic and healthy children by gas chromatography/mass spectrometry. Med Sci Monit. 2010;16(10):CR488–492.

Clinical Contributor
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Ramona Richard, MS, NC

Ramona Richard, MS, NC

Ramona Richard graduated with honors from the University of California with a Bachelor’s Degree in psychology and graduated summa cum laude with a Master’s Degree in Health and Nutrition Education. She also holds a Standard Designated Teaching Credential from the State of California, is a California state-certified Nutrition Consultant and a member of the National Association of Nutrition Professionals.

Ramona has participated in nutrition education in both public and private venues, including high school and college presentations, radio and public speaking for the past 20 years. She is the owner of Radiance, a nutrition consulting company, the Director of Education for Sanesco International, and a medical technical writer.

Disclaimer: The information provided is only intended to be general educational information to the public. It does not constitute medical advice. If you have specific questions about any medical matter or if you are suffering from any medical condition, you should consult your doctor or other professional healthcare provider.

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