Co-Occurring Mental Illness and Behavioral Support Needs in Adults with Intellectual and Developmental Disabilities.

People with intellectual and developmental disabilities (IDD) have higher incidences of mental health conditions and behavioral support needs than people without IDD but may not receive needed care from community providers. We examined rates of co-occurring conditions in a representative sample of adults with IDD who use state funded services in [state name redacted for peer review]. Using data from two datasets, we identified four categories of mental health and behavioral conditions. We used these categories to examine differences in individual- and system-level factors in people with and without co-occurring conditions. We found high rates of co-occurring conditions in our sample. We found important disability factors and system-level characteristics that were associated with having a diagnosed mental health condition or behavioral support needs. Differing patterns of diagnosis and treatment for co-occurring conditions suggests more work needs to be done to support people with IDD and co-occurring mental health conditions living in the community.