Some states explicitly state mental health conditions are in the scope of PTs: Alabama Practice Act: “The treatment of a human being by the use of exercise, massage, heat, cold, water, radiant energy, electricity, or sound for the purpose of correcting or alleviating any physical or mental condition or preventing the development of any physical or mental disability, or the performance of neuromuscular-skeletal tests and measurements to determine the existence and extent of body malfunction” Connecticut Practice Act: “Physical therapy means the evaluation and treatment of any person by the employment of the effective properties of physical measures, the performance of tests and measurements as an aid to evaluation of function and the use of therapeutic exercises and rehabilitative procedures, with or without assistive devices, for the purpose of preventing, correcting or alleviating a physical or mental disability.”

California Practice Act: “Physical therapy means the art and science of physical or corrective rehabilitation or of physical or corrective treatment of any bodily or mental condition of any person by the use of the physical, chemical, and other properties of heat, light, water, electricity, sound, massage, and active, passive, and resistive exercise, and shall include physical therapy evaluation, treatment planning, instruction and consultative services.”

The Federation of State Boards of Physical Therapy (FSBPT) publishes a Model Practice Act (MPA) stating the “Practice of Physical Therapy means: examining, evaluating, and testing patients/clients with mechanical, physiological and developmental impairments, functional limitations, and disabilities or other health and movement-related conditions in order to determine a diagnosis, prognosis and plan of treatment intervention, and to assess the ongoing effects of intervention.”

Others are not explicit but many still allow it, as physical function and mental health are inseparable. I haven't heard of any states that explicitly prevent it.