State spending on adults with autism is dramatically higher than for children, according to a new analysis that may offer hints of what’s to come as more people on the spectrum grow up.

In a study looking at per-person spending on autism services in California, researchers found that the state is shelling out roughly $26,500 on average for each adult annually. By comparison, costs for those under age 18 are averaging about $10,500.

“There are more children diagnosed today with autism than any time in history,” said Paul Leigh, a professor of public health sciences at the University of California, Davis, who led the study published in the journal PLOS One. “Our findings can help stakeholders, including legislators and health insurance administrators, accurately estimate the costs of autism services and plan their budgets to meet the lifelong need for those services.”

For the analysis, Leigh and his colleagues assessed spending by the California Department of Developmental Services during the 2012–2013 fiscal year.

The figures account for spending on more than 42,000 California residents on the spectrum for employment supports, transportation, residential placements at community care facilities, day care and respite care, but do not include medical expenses or costs incurred by schools.

As people with autism age, the analysis shows that state expenditures soared, with those over 18 receiving two-and-a-half times more in services as compared to younger people. At the widest extremes, the study indicates that California spends about $12,000 on those ages 3 to 6 compared to nearly $50,000 on individuals age 65 and over.

The greatest costs were associated with residential care and day care, the study found. There were also stark disparities by race with spending on white people with autism consistently exceeding that of Hispanic and African-American residents of all ages.

“As children with autism grow up and become adults and no longer receive public school-based assistance, their services transition to expensive independent living support and more of the cost burden shifts to the state,” Leigh said. “We hope our data can help justify earlier, expanded and equitable spending on younger children with autism. There is a great return on investment in high-quality early intervention services, which consistently have been found to reduce the disability associated with autism and to support the greater independence and integration in society as a whole of adults with autism.”