The bill amends the General Laws in Chapter 27-38.2, which pertains to insurance coverage for mental illness and substance use disorders, by introducing new definitions and clarifying existing ones to ensure a comprehensive understanding of these conditions within health insurance plans. It defines terms such as "financial requirements," "group health plan," "health insurance plan," "health insurers," "treatment limitations," and introduces the definition of "generally accepted standards of mental health and substance use disorder care." The bill expands the definition of "mental health and substance use disorders" to include conditions listed in the DSM and the International Classification of Diseases, and introduces "utilization review" processes. It also specifies exclusions from coverage, such as tobacco and caffeine, and requires coverage for medically necessary treatment of mental health and substance use disorders without limiting benefits to short-term or acute treatment.

The bill sets forth new requirements for insurers, including the application of the most recent level of care placement criteria and practice guidelines for utilization reviews, and prohibits the use of more restrictive criteria. Insurers must authorize a higher level of care if the recommended level is unavailable and must detail disagreements with service providers. It mandates insurers to provide education programs on clinical review criteria, ensure consistent decision-making through interrater reliability testing, and meet a minimum pass rate of 90% or undergo remediation. The bill includes provisions for civil penalties for violations, prohibits discretionary clauses in insurance contracts that could undermine state laws, and contains a severability clause. The act will take effect upon passage.