Each profession requires certain levels of training and experience and are regulated by their own licensing body. Under the Regulated Health Professions Act (RHPA), only those licensed by their College can use the title. For example, only individuals licensed by the College of Psychologists of Ontario (CPO) can call themselves Psychologists and say they provide “psychological” services.
In Ontario, only Psychologists and Medical Doctors can make mental health diagnoses.
In Ontario, Psychologists (C.Psych.) typically have earned a PhD in Psychology, have: completed coursework in a varied subjects; designed and carried out original research studies for their PhD dissertation; clinical placements & a one-year (2000-hr) predoctoral residency; an additional year of supervised practice under a registered psychologist; and comprehensive psychological and jurisprudence/ethics exams.
(Note: due to Canada’s Mutual Recognition Agreement, some Psychologists in Ontario are Masters-level trained.)
Psychologists are not usually covered under OHIP, with some exceptions when they work in hospital programs or on a Family Health Team (FHT).
Psychiatrists (RCPSC) are medical doctors (MD) who have completed medical school and a residency in Psychiatry. They can prescribe medication and are covered under OHIP.
In Ontario, Psychotherapists (RP) is a relatively newer designation in Ontario. RPs have at least a Bachelors degree, clinical experience, and pass a registration exam.
The Ontario Psychological Association (OPA) provides a useful overview of some of the differences between the professions: Profession Comparison Chart