Co-occurring ADHD Associated With Poorer Health Outcomes in Adults With Autism on Medicaid

Key Clinical Summary

• Attention-deficit/hyperactivity disorder (ADHD) was substantially more common among adults with autism enrolled in Medicaid, particularly those with co-occurring intellectual disability.
• Only about one-quarter of adults with ADHD received ADHD-indicated medications across all groups.
• Co-occurring ADHD was associated with higher rates of substance use, cardiovascular conditions, and injury, while ADHD medication use was linked to lower injury and cardiovascular risk.

Adults with autism experience poorer health outcomes than the general population, but the role of co-occurring ADHD has been underexplored. A large US population-based cohort study using Medicaid claims data examined ADHD prevalence, medication use, and associations with adverse health outcomes among adults with autism. The findings were published following analyses completed between September 2023 and September 2024.

Study Findings

Using national Medicaid data from 2008 to 2019, researchers analyzed 3 506 661 adults aged 18 years or older, including adults with autism with and without intellectual disability (ID), adults with ID without autism, and a random sample of Medicaid enrollees. The mean age was 33.5 years, and 52.9% were female.

ADHD prevalence was markedly higher in all neurodevelopmental groups compared with the general Medicaid population, in which 2.7% had an ADHD diagnosis. ADHD prevalence reached 26.7% among adults with autism without ID (prevalence ratio [PR], 5.1), 40.2% among adults with autism with ID (PR, 6.8), and 19.0% among adults with ID without autism (PR, 4.4).

Across all groups, 26.6% of adults with ADHD received an ADHD medication prescription. Co-occurring ADHD was consistently associated with worse health outcomes. For example, 13.2% of autistic adults with ADHD had a substance use disorder compared with 5.7% of autistic adults without ADHD.

ADHD diagnoses were linked to higher rates of substance use, cardiovascular conditions, and injury regardless of diagnostic group. However, among individuals with ADHD who received ADHD medications, rates of injury and cardiovascular conditions were lower across all groups. Substance use remained higher among individuals with ID who had ADHD diagnoses and medication prescriptions.

Clinical Implications

These findings highlight ADHD as a significant driver of poor health outcomes among adults with autism in the US Medicaid system. For payers and managed care organizations, the results underscore the importance of identifying and treating ADHD in this population as part of comprehensive care strategies.

Medicaid plays a central role in financing care for adults with autism across the lifespan, including behavioral health, developmental disability services, and medication management. Suboptimal coordination across service siloes may contribute to untreated ADHD and downstream health risks. The observed association between ADHD medication use and lower rates of injury and cardiovascular conditions suggests that appropriate pharmacologic treatment may mitigate some health risks.

From a policy perspective, the study points to opportunities to strengthen care coordination, expand coverage for medication management, and integrate behavioral and physical health services. State-level variation in Medicaid delivery models may offer pathways to improve outcomes through targeted reforms.

“Our findings emphasize the importance of co-occurring ADHD on the health safety of autistic adults,” the authors wrote. They noted that access to and coverage of ADHD medications “supports optimal outcomes among autistic adults,” particularly within Medicaid, which is “critical in providing access to and delivery of supports for ADHD, ID, and autism, including medication management, substance use treatment, home- and community-based services, and neurodevelopmental care…”

Conclusion

In this national Medicaid cohort, adults with autism had high rates of co-occurring ADHD and elevated risks of adverse health outcomes. ADHD medication use was associated with lower injury and cardiovascular risk, suggesting that improved identification and treatment of ADHD may meaningfully improve health outcomes for adults with autism.

Reference

Yerys B, Tao S, Shea L, Wallace GL. Attention-deficit/hyperactivity disorder in medicaid-enrolled autistic adults. JAMA Netw Open. 2025;8(2):e2453402. doi:10.1001/jamanetworkopen.2024.53402