It’s confusing isn’t it? Let’s bring some clarity here.
Psychiatrists are medical doctors (MD’s) with a focus on mental health. They can formally diagnose and prescribe medications.
Psychologists are “doctors of psychology” but are not medical doctors. They have a PhD. They are allowed to diagnose mental health conditions, conduct psychological assessments, but cannot prescribe medications.
Psychotherapists and Clinical Counsellors are interchangeable designations where each province will have certain protected rights to use a particular designation. For example, in British Columbia, we are called either Registered Clinical Counsellors or Certified Clinical Counsellors; in Ontario the term used is Registered Psychotherapist. Counsellors/Psychotherapists (whichever term is used) generally have a MA level degree, are able to conduct psychological /counselling services but are not able to formally diagnose, assess, or prescribe medication.
Social Workers are able to conduct counselling sessions and are governed by the College of Social Workers. They may also belong to other professional associations and conduct therapy/counselling/psychotherapy within those guidelines.
Social workers most often have a MA level degree, and like Clinical Counsellors/Psychotherapists, cannot formally diagnose, assess, or prescribe medication.
Hope that helps!