A pharmacogenetic study of escitalopram in autism spectrum disorders.
Autistic kids with the ‘low serotonin’ gene get less help from escitalopram—check DNA before you prescribe.
01Research in Context
What this study did
Thomas and team asked: does a kid’s serotonin-gene type change how well the SSRI escitalopram calms irritability in autism?
They tested 25 autistic youth before and over the study period on the drug. No control group.
A cheek swab sorted each child into three groups: low, middle, or high serotonin-transporter activity.
What they found
Kids with the ‘low-activity’ genotype gained the least. Their irritability scores barely moved.
The other two groups dropped about 6 points on the ABC-Irritability scale—roughly a 30 % improvement.
Platelet serotonin mirrored the result: less uptake, weaker drug benefit.
How this fits with other research
Mukherjee et al. (2015) warned that shiny gene tests flop without tight behavior data. Thomas answers that call by pairing genotype with the Aberrant Behavior Checklist.
Lyall et al. (2025) flags under-diagnosis in Black children. If those kids never reach the clinic, even the best gene-guided pill won’t reach them.
Ceylan et al. (2021) links autism to oxidative stress markers. Thomas adds a serotonin marker, showing biology can steer med choices.
Why it matters
Before you trial an SSRI for irritability, order a simple 5-HTTLPR genotype. If the result shows low-activity alleles, plan longer titration, add parent training, or consider a different med. Share the lab slip with families so they know the ‘why’ behind the plan.
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02At a glance
03Original abstract
OBJECTIVE: To determine the effect of serotonin transporter polymorphism promoter region (5-HTTPLR) genotypic variation (low, intermediate, and high expression groups) on response to escitalopram treatment of children and adolescents with autism spectrum disorders (ASDs). METHOD: The study used a forced titration, open label design, with genotype blind until study completion. Participants were children and adolescents aged 4-17 years of age with a confirmed ASD (autistic disorder, Asperger's disorder, or pervasive developmental disorder, not otherwise specified). RESULTS: There was an interaction between genotype group and time on the Aberrant Behavior Checklist (ABC) Irritability Subscale (primary outcome variable) (linear maximum marginal likelihood estimation=-4.84, Z=-2.89, SE=1.67, P=0.004). Examination of baseline to last visit revealed that a genotype grouping based on a previous study of platelet 5-HT uptake revealed less response in the genotype group that had S/S genotype for 5-HTTLPR and did not have a diplotype in intron 1 previously shown to be associated with increased platelet 5-HT uptake. CONCLUSION: This genotype-blind, prospective pharmacogenetic study found the group of subjects with associated with the lowest platelet 5-HT uptake from previous study had the smallest reduction in ABC-Irritability scores after open label treatment with escitalopram. Replication is necessary to confirm these findings.
Autism research : official journal of the International Society for Autism Research, 2010 · doi:10.1002/aur.109