Despite limited evidence supporting the practice, researchers say nearly two-thirds of children with autism are taking at least one psychotropic drug.

In a review of medical and pharmacy claims data for 33,565 kids with autism between 2001 and 2009, researchers found that 64 percent of children on the spectrum were prescribed at least one psychotropic medication.

What’s more, the study published online Monday in the journal Pediatrics, found that 35 percent of kids with the developmental disorder were given two or more types of drugs simultaneously and 15 percent were taking at least three.

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Older children and those with co-occurring conditions like seizures, attention-deficit disorders, anxiety, bipolar disorder or depression were more likely to be taking psychotropic drugs, the study found.

Meanwhile, children with autism living in the Northeast and West were less likely to be taking medication while those in the South had higher odds of being prescribed one or more psychotropic drugs, the findings indicated.

The regional trends may point to a lack of behaviorally-based treatment options in some areas of the country, the researchers said.

“Despite minimal evidence of the effectiveness or appropriateness of multi-drug treatment of ASD, psychotropic medications are commonly used, singly and in combination, for ASD and its co-occurring conditions,” wrote the team of researchers from Drexel University, OptumInsight, The Lewin Group and OptumHealth Behavioral Solutions in the study. They said the findings point to an immediate need to establish “standards of care” around the presciption of psychotropic medications for those with autism.

A previous study of more than 60,000 children with autism insured by Medicaid found that 56 percent were taking psychotropic medications. The findings are similar to those of the current study — which included only privately-insured kids — suggesting that children with autism are being advised to take the drugs at similar rates regardless of their insurer, the researchers said.