The different schools of therapy have different philosophies about the length of therapy. Cognitive-behavioral therapies tend to be short term, while humanistic and psychodynamic therapies tend to be longer. Psychoanalysis often goes on for many years. Research suggests that minor and relatively recent problems may not require long-term treatment while more severe, complex and long lasting problems will take more time. The length of the treatment also depends on the preferences of the patient.

Some patients are happy with resolution of the presenting symptom and choose to stop treatment as soon as there is symptomatic improvement. Other patients are interested in greater self-exploration and personality development, and stay in therapy much longer. In the 1995 Consumer Reports study, patients who stayed in therapy longer tended to be more satisfied with their treatment. Of course, this could reflect a selection bias because people who were more satisfied with their treatment may have chosen to stay in therapy longer.