The U.S. will release long-awaited rules today requiring insurers to cover treatment for mental illness in the same manner they provide care for physical health, a senior administration official said.

The regulations, five years in development, mean that insurance companies won’t be able to charge higher co-payments or deductibles for treatment of mental illness or limit the duration of care any more than they would for treatment of a physical condition.

The requirements will apply to almost all health plans in the nation including new ones sold under the health-care overhaul, the Patient Protection and Affordable Care Act of 2010.

The administration also considers the rules to be a chief component of an effort to reduce gun violence, the official said.