The bill amends Chapter 27-38.2 of the General Laws, which pertains to insurance coverage for mental illness and substance use disorders, by introducing new definitions and terms to clarify coverage scope. It adds definitions for terms such as "financial requirements," "group health plan," "health insurance plan," "health insurers," "mental health or substance use disorder," "non-quantitative treatment limitations," "quantitative treatment limitations," "generally accepted standards of mental health and substance use disorder care," "medically necessary treatment," "mental health and substance use disorders," and "utilization review." The bill specifies that "mental health and substance use disorders" include conditions listed in the DSM or ICD, and that "utilization review" refers to the process of approving, modifying, or denying coverage based on medical necessity. It also requires that medical necessity determinations and utilization review criteria be based on current generally accepted standards of care, with denials and appeals reviewed by a professional with the same level of education.

The bill imposes new coverage requirements for insurers, effective January 1, 2025, to provide coverage for medically necessary treatment of mental health and substance use disorders without limiting benefits to short-term or acute treatment. It prohibits rescinding or modifying authorized treatments after they have been provided and requires coverage for out-of-network services when in-network options are not timely or geographically accessible. Insurers are barred from limiting benefits based on potential coverage by public entitlement programs and from adopting policy terms that conflict with the new requirements. The bill also mandates that insurers use the most recent level of care placement criteria and practice guidelines from professional associations for utilization reviews, sponsor education programs about clinical review criteria, and achieve a minimum interrater reliability pass rate of 90% in decision-making. Violations may result in civil penalties, and the bill includes a severability clause and prohibits discretionary clauses in insurance contracts that could undermine state laws. The act takes effect upon passage.