People having psychotherapy quite often make sudden gains, displaying abrupt and substantial improvements in symptoms from one session to the next. Sudden gains have been investigated in the context of randomised controlled trials (RCTs), tightly-controlled studies designed to compare one treatment with another, and in therapy carried out by experts but researchers from American University in Washington D.C. looked to see whether these gains could occur in other contexts. They studied 106 outpatients being treated in a university-based psychotherapy training clinic. Overall sudden gains were identified in 29% of the patients, gains which tended to occur early in therapy. However, the gains were more likely to be reversed than in RCTs which usually involve more-experienced therapists. 54% of the sample showed gradual gains which tended to occur later in therapy. Those patients who had had sudden gains did significantly better by the end of therapy than those who showed more gradual gains.
Greenfield, M. F., Gunthert, K. C. and Haaga, D. A. - Sudden gains versus gradual gains in a psychotherapy training clinic Journal of Clinical Psychology n/a. doi: 10.1002/jclp.20748