More psychiatric hospitals are working to meet the needs of a burgeoning population of kids with autism and other developmental disabilities, a new study finds, but despite significant growth, services remain limited.

Researchers found just nine hospital units across the country that focus specifically on the needs of those with autism and other developmental disorders. That’s more than twice the number that existed 10 years ago.

Nonetheless, the specialized programs are far from meeting the national need, accounting for just 137 beds at psychiatric hospitals. Most of the facilities are concentrated in the Northeast and none are located west of Denver, according to the study published in the Journal of Autism and Developmental Disorders late last month.

Researchers surveyed officials at all of the specialized facilities and found that kids are most often admitted due to problems with aggression, self-injury or elopement. All nine units reported employing both child psychologists and behavioral specialists to best meet the children’s unique needs.

But the biggest challenge the hospitals face is finding adequate services for the children once they are discharged from inpatient settings, according to the study led by Matthew Siegel of the Tufts University School of Medicine.