This is a very commonly asked question, but one that is difficult to answer precisely. Therapy can last for just a few sessions (solution- focused ) or for many years (psychoanalysis). It depends on the type of therapy, the nature of your problem as well as your goals for therapy.
Ultimately, you have the choice and can decide how long you wish to work with a therapist. You may prefer a long-term, broader and more in depth approach; whereas others look to having fewer sessions to work on a specific issue. This can be followed up if and when it is needed.
The main differences between these three mental health care workers is their training and educational background. Despite these differences, all three can be psychotherapists!
A psychiatrist is a medically trained doctor, who has specialized in psychiatry. He/she can prescribe medication.
A psychologist has a four year psychology degree and has done an internship. He/she cannot prescribe medication. A counsellor does not need to have an undergraduate degree in either medicine or psychology. They cannot prescribe medication. counsellors generally work with problems of normal living rather than severe mental illness.