Neurochemical correlates of autistic disorder: a review of the literature.
Brain-chemistry studies in autism are still messy—serotonin leads the pack, but no lab value yet drives clinical choices.
01Research in Context
What this study did
Lecavalier et al. (2006) read every paper on brain chemicals and autism. They looked at serotonin, dopamine, GABA, and more. The team only summarized past work; they did not run new lab tests.
They included kids and adults diagnosed with autism. No drug trials or behavior plans were tested.
What they found
Serotonin had the clearest link to autism, but even those studies clashed. Other chemicals showed weaker or mixed results. Most papers had tiny samples and poor controls.
The authors warned that strong claims about brain chemistry and autism were still premature.
How this fits with other research
Pan et al. (2021) later pooled data from many labs. They found autism travels with epilepsy, macrocephaly, and cerebral palsy far more often than chance. Their wider lens shows the serotonin clue is only one piece of a bigger neurological puzzle.
Hudson et al. (2012) checked if any pills that tweak these chemicals actually help kids. Only a few meds passed the RCT bar, and even those effects were small. So the mixed chemistry picture in Lecavalier et al. (2006) still holds: lab findings have not yet become solid drug targets.
Hu et al. (2017) moved the hunt downstream to microRNAs. These tiny gene switches also look altered in autism, pointing to newer molecular markers beyond classic transmitters. Together the reviews chart a path from old single-chemical guesses to multi-level biology.
Why it matters
For now, brain-chemistry tests are not ready to diagnose autism or guide meds. Keep using gold-standard behavior tools and watch for neurological red flags like seizures or head-size jumps. Track future biomarker work, but base today’s treatment plans on skills, not spinal taps.
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02At a glance
03Original abstract
Review of neurochemical investigations in autistic disorder revealed that a wide array of transmitter systems have been studied, including serotonin, dopamine, norepinephrine, acetylcholine, oxytocin, endogenous opioids, cortisol, glutamate, and gamma-aminobutyric acid (GABA). These studies have been complicated by the fact that autism is a very heterogeneous disorder which often presents with comorbid behavioral problems. In addition, many of these studies employed very small samples and inappropriate control groups, making it difficult to draw conclusions with confidence. Overall, serotonin appears to have the most empirical evidence for a role in autism, but this requires further investigation and replication. There is little support for the notion that a dysfunction of norepinephrine or the endogenous opioids are related to autism. The role of dopaminergic functioning has not been compelling thus far, though conflicting findings on central dopamine turnover require further study. Promising new areas of study may include possible dysfunction of the cholinergic system, oxytocin, and amino acid neurotransmitters. Implications for pharmacotherapy are briefly discussed for each neurotransmitter system with brief research examples. Review of this work emphasizes the need for future studies to control for subject variables, such as race, sex, pubertal status, and distress associated with blood draws, which can affect measures of neurochemical function. In addition, research in neurochemistry must continue to work in concert with other subspecialties to form a more comprehensive and theory-based approach to the neurobiological correlates of autistic disorder.
Research in developmental disabilities, 2006 · doi:10.1016/j.ridd.2005.03.003