Hyperserotoninemia and altered immunity in autism.

Schneider et al. (2006) wrote a narrative review. They pulled together papers on two things: high blood serotonin and immune problems in autism.

They did not run new experiments. They summarized what others had found up to 2006.

About one in three autistic people have high blood serotonin. The same group often shows immune oddities like different T-cell counts.

The review does not give treatment data. It only flags the link so clinicians stay alert.

Older studies already saw the same signals. Martens et al. (1989) showed high serotonin runs in families. Warren et al. (1986) first listed immune skew in autism. The 2006 review stitches these threads together.

Later work adds new layers. Oblak et al. (2013) moved from blood to brain, finding fewer serotonin receptors in social areas. Lim et al. (2016) traced immune activation to a glutamate pathway. Zhou et al. (2018) found high stool IgA, pointing to gut immunity.

Lecavalier et al. (2006), a twin review from the same year, agrees serotonin has the strongest evidence but warns most studies are small and weak. The papers do not clash; they simply echo the need for tighter methods.

You cannot fix serotonin or immunity with ABA, but knowing these patterns helps you read medical charts. If a client has frequent infections or GI issues, share the blood serotonin and immune labs with the pediatrician. The data may speed up referrals and keep biological pain from worsening behavior.