The Dose Response Relationship in Psychotherapy: Implications for Social Policy

The principle aim of this study was to estimate the number of sessions of psychotherapy needed for clients suffering from psychiatric illness to return to a normal state of functioning or reliably improve. This would be helpful for treatment planning and policy decisions regarding how much therapy is enough. The progress of 125 clients entering psychological treatment in two university training clinics was tracked on a session-by-session basis using a naturalistic design. Recovery and reliable improvement were the bi-nomial events of interest used in a survival analysis that estimated the number of weekly treatment sessions needed to meet criteria. Using survival analysis it was estimated that it would take about 8 sessions for 50% of clients to show reliable improvement and 21 sessions for about 85% to meet this criterion. Recovery took more treatment, with 50% of clients estimated to recover after 14 sessions and 70% requiring 23. On the basis of the present results we conclude that the present policy of the Australian Government in both the public and private sector regarding the number of sessions needed for clients entering psychological treatments to show a benefit is much less than is, in fact, necessary. The findings of the current study are roughly consistent with those found elsewhere and suggest a minimum benefit should be closer to 20 sessions. The current policy appears to be suitable for only about one-third of clients who carry the burden of psychological illness. (Contains 3 figures.)