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Nordmo, M., Monsen, J.T., Høglend, P.A., & Solbakken, O.A. (2020) Investigating the dose–response effect in open-ended psychotherapy. Psychotherapy Research

Findings form psychotherapy research studies have tested a dose-response relationship that shows that after a certain number of sessions the rate of client improvement diminishes. That research tends to show a range of 4 to 12 sessions is necessary in order for the average client to improve (half of clients get better by this point, but half do not yet get better). The key limitation of this research is that the vast majority of it was conducted in student counselling centres offering brief treatments. That is, the clients in this research domain tend to be students with mildly to moderately severe problems, and the counselling centres often had a policy (not based on client need) that limited the number of treatment sessions. There is actually very little psychotherapy dose-response research of clients with moderate to severe problems who receive treatment in naturalistic settings that do not arbitrarily impose a session limit. In such settings, it would be the client’s optimal response to treatment and not externally imposed limits that determine when therapy is terminated. This study by Nordmo and colleagues was conducted in several psychotherapy outpatient clinics in Norway. The 362 adult clients had moderate to severe levels of mental health problems, and about half had a personality disorder. The 88 therapists had about 10 years of experience and used several major orientations of psychotherapy practice (psychodynamic, CBT, behavioral, humanistic). Clinicians and clients came to an agreement about when to terminate therapy, and so no limit on sessions was externally imposed. Outcomes were assessed regularly and were evaluated for reliable change and clinical recovery in symptoms and interpersonal problems. Clients attended an average of 52 sessions (SD = 59, Mdn = 36), and improvements were maintained up to 2 years post-treatment. The results indicated that the more sessions a client received the greater their improvement. This was particularly true for those clients with more severe problems. Clients with less severe problems needed fewer sessions to improve. The average client needed 57 sessions to show clinically significant improvement.

Practice Implications

The psychotherapy dose-response research to date is limited because it is primarily based on clients with mild to moderate problems treated in student counselling centres. In real-world contexts, client rate and magnitude of change are related to the length of treatment. That is, clients with moderate to severe problems will require more than 4 to 12 sessions in order to improve. As the authors argued, the one-size-fits-all approach to treatment length in everyday practice is not supported by the research, and does not provide adequate treatment to those clients with moderate to severe problems, or those with complex comorbidities.

Erekson, D.M., Lambert, M.J., & Egget, D.L. (2015). The relationship between session frequency and psychotherapy outcome in a naturalistic setting. Journal of Consulting and Clinical Psychology.

The dose-response model of psychotherapy suggests that a single session is like a “dose” of therapy, and that each session adds to a cumulative response by the client. For example, research indicates that between 13 and 18 sessions are required for 50% of patients to improve significantly, but with diminishing returns for clients after 18 sessions. In this very large study in a naturalistic setting, Erekson and colleagues studied the question of the effects of the “dose” or quantity of therapy a little differently. What if the spacing or frequency of sessions rather than the total number of sessions was important to patient outcomes? That is, if psychotherapy reinforces adaptive behaviors, then less learning might occur if time between sessions increases. With greater time between sessions clients may miss timely support from a therapist, and the therapeutic alliance may not be as solid. Erekson examined the impact of session frequency in a very large sample of university students (N = 21,488) seen by therapists (N = 303) for individual therapy lasting about 50 minutes per session. Clients typically received between 6 and 21 weeks of therapy. The data were collected at a counselling center over a 17-year period. Therapist orientations included CBT, psychodynamic, existential, and integrative. Patient outcomes were measured after each session with a reliable measure that allows one to evaluate if a client recovered from symptoms, reliably improved but did not recover, or reliably deteriorated. The authors found that compared to less frequent sessions (approximately every 2 weeks), more frequent sessions (approximately weekly) was associated with faster improvement and faster recovery. The statistical models predicted that 50% of individuals being seen weekly would reliably improve in 8 sessions, whereas 50% those seen every 2 weeks would reliably improve in 12 sessions. That is, clients seen every two weeks required 50% more sessions to achieve the same level of improvement as clients seen every week.

Practice Implications

Clients that are seen weekly may have a better therapeutic experience and develop a better therapeutic alliance with their therapists, which may in turn result in faster improvements. More frequent meetings may suggest to clients that their needs are important to the therapist. Institutions may have the opinion that lower session frequency is a way of saving resources, but in the end patients seen less frequently may require more therapy to achieve outcomes at the same rate as patients seen more frequently. Higher frequency of sessions may increase the efficiency of the psychotherapy and possibly reduce the amount of resources invested by the institution to improve patient mental health outcomes.

Stiles, W.B., Barkham, M., & Wheeler, S. (2015). Duration of psychological therapy: Relation to recover and improvement rates in UK routine practice. British Journal of Psychiatry, 207, 115-122.

In this very large study from the UK National Health Service (NHS), Stiles and colleagues assessed whether more therapy is better. That is, do people continue to get better with more sessions or do patients reach a certain level of improvement and terminate therapy regardless of number of sessions. The “dose-effect model” of psychotherapy suggests that patients continue to improve with more sessions, although the rate of improvement slows down after 18 sessions. However, large naturalistic studies from the UK health system show that patients have similar rates of recovery regardless of the number of sessions they attend (i.e., up to 20 sessions). These findings suggest that patient improvement may follow a good-enough or “responsive regulation model” of improvement, in which patients responsively regulate the number of sessions that they need. This could have implications for policies regarding how many sessions are prescribed to patients. In this study, Stiles and colleagues drew data from the NHS data base of over 26,000 adult patients who were seen by 1,450 therapists. These were patients who provided enough reliable outcome data, who attended 40 or fewer sessions, and who had a planned ending. Many patients had multiple problems including anxiety, depression, bereavement, and trauma and abuse. Patients who were selected for the study had initial symptom scores in the clinical range. The most common therapy approaches included integrative, psychodynamic, CBT, and supportive. Patient “recovery” was defined as no longer scoring in the clinical range at the end of therapy. Patient “improvement” was defined as a reliable drop in symptom scores on a psychometric measure. Patients received an average of 8.3 sessions, 60% recovered, and an additional 19% improved but did not recover. Rates of reliable improvement were negatively correlated (r = -.58) with number of sessions, and the effect was large. That is, patients who stayed in therapy longer had lower rates of recovery. These patients were more symptomatic at the outset.

Practical Implications

The results of this very large naturalistic study suggest that therapists and clients should regularly monitor improvement and adjust the treatment duration based on whether clients improve to a satisfactory level. The authors refer to this as “responsive regulation” of treatment duration. In practice, this means that therapists and clients end treatment when patients have improved to a “good-enough” level, which is likely balanced against costs and alternatives. These findings should encourage therapists and agencies to shift their attention away from prescribing a pre-specified length of treatment at the beginning of therapy towards evaluating on an ongoing basis what constitutes good-enough gains for each client.

Abbass, A., Kisely, S., Rasic, D., Town, J.M., & Johansson, R. (2015). Long-term healthcare cost reduction with Intensive Short-term Psychodynamic Psychotherapy in tertiary psychiatric care. Journal of Psychiatric Research, http://dx.doi.org/10.1016/j.jpsychires.2015.03.001

Several years ago Lazar (2010) published a book detailing the cost-effectiveness of psychotherapy for a variety of disorders. That is, her systematic review found that on most economic indicators (lost income, decreased disability, decreased health utilization) psychotherapy resulted in an immediate cost reduction over and above the cost of the treatment. In this study from Halifax, Canada, Abbass and colleagues looked at the effects of psychotherapy, specifically of Intensive Short-term Dynamic Psychotherapy (ISTDP), on the long-term reduction in hospital costs and physician visits. Abass and colleagues argue that adverse childhood events are an important determinant of adult mental health problems and of increased costs to the health system likely because of the consequence of problems with emotion regulation. Psychotherapies like ISTDP specifically address issues that are a consequence of childhood maltreatment and so might reduce some of the consequent health care costs. Abbass and colleagues provided ISTDP to 890 patients in the Halifax health care system who were referred to the psychotherapy service from emergency departments, physicians, and mental health providers. These patients’ outcomes were compared to 192 patients not seen by the clinic for various reasons. Most common diagnoses of the total sample were: somatoform disorder, anxiety disorder, personality disorder, and depressive disorder. Participant completed measures of psychological distress, and the research team were able to access provincial health usage data tracked over 3 years. Fifty eight therapists of various skill levels (psychiatrists, psychologists, family physicians, trainees) provided ISTDP. The average patient attended 7.3 sessions which cost $708 (estimated by salaries in 2006). Patients receiving psychotherapy had physician and hospital costs that decreased from $3,224 to $4759 in Canadian dollars per year over three years (again in 2006 dollars). Patients in the control condition not receiving ISTDP showed health care costs that increased from $368 to $2,663 per year. These trajectories of health care costs were significantly different. Yearly physician and health care costs for patients prior to being treated with ISTDP were greater than those of the general Canadian population, but 3 years post ISTDP their health care costs were less than the general Canadian population. In addition, compared to control patients those treated with psychotherapy showed a significant reduction in psychological distress.

Practice Implications

This study by Abbass and colleagues demonstrates that short term psychotherapy provided to a broad range of patients and targeting health and illness behaviors related to problems with emotion regulation can reduce health care costs. These reductions in hospital and physician visits occurred in the short term and were sustained over several years. Some patients may require longer treatment, but the evidence suggests that short term interventions should be tried first.

Author email: allan.abbass@dal.ca