The psychotherapy dose-response effect and its implications for treatment delivery services.

TLDR

Few studies have examined the dose–response relationship, but consensus indicates that 13–18 therapy sessions are needed for half of patients to improve. Controlled trials show 57.6–67.2% of patients improve after about 12.7 sessions, whereas naturalistic data from over 6,000 patients reveal an average of fewer than five sessions and only ~20% improvement, indicating that most patients receive insufficient exposure and recover at lower rates than in trials.

Abstract

To date, few studies have been published on the doseresponse relationship, but there is general consensus that between 13 and 18 sessions of therapy are required for 50% of patients to improve. Reviewing the clinical trials literature reveals that in carefully controlled and implemented treatments, between 57.6% and 67.2% of patients improve within an average of 12.7 sessions. Using naturalistic data, however, revealed that the average number of sessions received in a national database of over 6,000 patients was less than five. The rate of improvement in this sample was only about 20%. These results suggest that patients, on average, do not get adequate exposure to psychotherapy, nor do they recover from illness at rates observed in clinical trials research.