Up to 1 in 3 Medicaid expansion enrolees in Iowa, New York, Washington, and West Virginia received behavioral health treatment in 2014. The two most commonly used types of behavioral health services used were diagnostic and psychotherapy services. These findings were reported in "Medicaid Expansion: Behavioral Health Treatment Use in Selected States in 2014" by the United States Government Accountability Office (GAO). The GAO selected the four expansion states listed above, and analyzed Medicaid data on behavioral health diagnoses and treatment use for expansion enrollees. They also analyzed documentation and interviewed Medicaid officials from these selected states to understand how . . .