A certified health service provider in psychology means a person licensed to practice psychology who has a doctoral degree in psychology, or prior to July 1, 1984, was licensed at the doctoral level with a degree in psychology or its equivalent, or was prior to January 1, 1984, licensed as a psychologist in this state and prior to January 1, 1985, receives a doctoral degree equivalent to a doctoral degree in psychology, and who has at least two years of clinical experience in a recognized health service setting or meets the standards of a national register of health service providers in psychology. A person certified as a health service provider in psychology shall be deemed qualified to diagnose or evaluate mental illness and nervous disorders, and to treat mental illnesses and nervous disorders, excluding those mental illnesses and nervous disorders which are established as primarily of biological etiology with the exception of the treatment of the psychological and behavioral aspects of those mental illnesses and nervous disorders.