Association of serotonin concentration to behavior and IQ in autistic children.

The team drew blood from the kids with autism. They checked how much serotonin stayed inside the platelets.

Next they gave each child an IQ test and the Autism Behavior Checklist (ABC). They asked: do kids with more serotonin score lower or higher?

Serotonin numbers did not line up with IQ or total ABC scores. The link was basically flat.

Only four single ABC items showed a weak trend: kids rated as "more severely affected" had slightly higher serotonin.

Ahlborn et al. (2008) repeated the idea in Curaçao. They also found high serotonin in some kids with PDD, but it did not track with gut permeability. Together the two papers show serotonin keeps missing behavior targets.

Varela et al. (2023) swapped serotonin for salivary cortisol. They saw IQ predict parent anxiety yet cortisol stayed quiet. The pattern echoes S et al.: one biomarker rarely tells the autism story.

Eussen et al. (2016) step back a generation. Moms who carry the short 5-HTTLPR serotonin gene plus prenatal stress raise ASD risk. So serotonin matters before birth, but once the child is here, platelet levels do not guide day-to-day behavior.

You can stop hunting for quick serotonin shortcuts. IQ and global severity are shaped by many roads, not one blood value. Keep using direct skill assessments and ABC interviews. If a doctor orders platelet serotonin, explain to families it is research-only and will not change the behavior plan today.