The Michelle Alyssa Go Act proposes to amend title XIX of the Social Security Act, specifically revising the definition of an institution for mental diseases (IMD) under the Medicaid program. Currently, Medicaid generally prohibits federal reimbursement for services provided to adults aged 21-64 in IMDs, which are facilities primarily engaged in treating mental diseases. This legislation would create an exception, excluding hospitals, nursing facilities, or other institutions from the IMD definition if they meet two specific criteria. First, the institution must have 36 beds or less . Second, it must adhere to nationally recognized, evidence-based standards for mental health programs, and for substance use disorder programs if applicable, as approved by the Secretary. These required standards include criteria for the types of services offered, hours of clinical care, and staffing credentials. The bill specifies that such standards could be those set forth by organizations like the American Society of Addiction Medicine for substance use disorder programs. The amendments made by this Act would take effect 180 days after enactment and apply to State plans from that date.