Researchers from the State Health Care Spending Project -- a collaboration between The Pew Charitable Trusts and the John D. and Catherine T. MacArthur Foundation -- sought to better understand the country's mental health challenges and, in particular, the states' role in addressing them. The project found that:In 2013, approximately 44 million adults -- 18.5 percent of the population 18 and older -- were classified as having a mental illness. Of these, 10 million had a serious mental illness. The rate of serious mental illness varied from state to state.In 2009, the most recent year for which national mental health data are available, 147billionwasspentonmentalhealthtreatmentintheUnitedStates.Amajorityofthespending,60percent,camefrompublicsourcessuchasMedicaid,stateandlocalgovernments,Medicare,andfederalgrants.Privatesources,includinghealthinsuranceandindividualout−of−pocketspending,madeupthedifference.Fundingfromstatesandlocalitiestotaled22 billion (15 percent) in 2009. This total does not include state and local Medicaid expenditures. Counting those contributions brings total state and local spending up to $35.5 billion (24 percent).This report is intended to help federal, state, and local policymakers working to address the country's mental health challenges to better understand their prevalence, treatment, and funding trends