Handbook of Psychotherapy and Behavior Change: Starting in March 2013 I will review one chapter a month in the Handbook of Psychotherapy and Behavior Change in addition to reviewing psychotherapy research articles. Book chapters have more restrictive copy right rules than journal articles, so I will not provide author email addresses. If you are interested, the Handbook table of content can be viewed on Amazon.
Lambert, M.J. (2013). The efficacy and effectiveness of psychotherapy. In M.J. Lambert (Ed.) Bergin and Garfield’s handbook of psychotherapy and behaviour change (6th ed.), pp. 169-218. Hoboken, N.J.: Wiley.
An important issue for patients, therapists, and agencies is the optimal dosage of psychotherapy that is necessary to reduce impairment and improve life functioning. In this part of the Handbook chapter on Efficacy and Effectiveness of Psychotherapy, Lambert tackles the issue of the psychotherapy dose-response relationship by reviewing the existing literature. That literature tends to focus on naturalistic national (U.S.) samples of patients (often N > 6,000) receiving routine care in Health Maintenance Organizations, Employee Assistance Programs, and Community Mental Health Clinics. Outcomes tend to be assessed by patient self report, and can include symptoms, character traits, quality of life, and interpersonal functioning, among others. Lambert defines “improved” patients as those who reliably changed but still are within the dysfunctional range on a measure, and he defines “recovered” patients as those who both reliably improved and were no longer in the dysfunctional range. He concluded that on average 50% of patients who begin treatment in the dysfunctional range achieve recovery following 21 sessions of psychotherapy. On the flip side, half of patients do not achieve recovery after 21 sessions. Almost 50 sessions are necessary for 75% of patients to recover. In other words, there is a rapid rate of recovery in which half of patients recover after 21 sessions, but then the rate of recovery slows down so that it takes up to 50 sessions for an additional 25% of patients to recover. The rates of recovery also differ depending on what is measured. Symptoms (depression, anxiety, etc.) tend to recover more quickly than characterological or interpersonal problems. Further, some patients experience sudden symptom gains in therapy that are long lasting. Between 17% and 50% of patients experience the majority of their symptom improvements within 7 sessions, and these early changes accounted for 50% of total symptom gains in therapy.
The question of how much therapy is enough is important for practical and theoretical reasons. Research on this topic can help patients, therapists, and agencies make decisions about treatment planning. Research suggests that a sizeable proportion of patients (50%) reliably improve after 7 sessions and a similar percentage recover after 21 sessions. However, limiting treatment to less than 20 sessions will mean that about half of patients will not achieve a substantial benefit from therapy. Session limits need to be assessed carefully depending on how the patient is doing and what outcomes are important or valued. Agencies or clinicians that firmly set limits on the number of psychotherapy sessions that are too low will have the majority of their patients showing some improvement but not recovering.