Co-occurring disorders have historically been defined as mental health and chemical dependency issues. Mental health providers have developed programs to help treat such co-occurring disorders. Chronic physical or severe illnesses have also been correlated to the development of both mental health issues and chemical dependency. These severe illnesses, such as HIV/AIDS and Cancer can be the threshold issue that leads to the development of both mental health and chemical dependency issues. Mental health agencies and mental health counselors should be aware of the potential for a chronic or severe physical health issue to lead to other illnesses, including mental health and chemical dependency. Counselors and agencies should be able to coordinate services to ensure the best holistic care for clients.