Cooper, M. (2010). Essential Research Findings in Counselling and psychotherapy.London: SAGE

The effect of therapy can be measured by a method where the client fill out a questionnaire about psychological distress before and after the therapy. These kinds of study primarily shows that therapy is effectual. However one can never be sure that the improvement is caused be spontaneous remission, and therefore it is important to compare the results with the results of a control group. The improvement can still be found, but it is smaller. The studies must be controlled for placebo as well, which also reduces the effect. Effect sizes in studies like this is about 0.75-0.85.

Effect size: the strength of the relationship between two variables.

Cohens d:

d = 0.2 = small effect size

d = 0.5 = medium effect size

d = 0.8 = big effect size

clinically significant improvement; the number of clients that enters therapy with a abnormally high level of psychological distress and leaves therapy with a level within the normal interval.

Effectiveness; the extent to which an intervention under normal conditions gives the desired effect. Kan be investigated by clients self-reports.

5-10% of clients conditions worsens during therapy, 10-15 % if it is race dependent. This must be compared to >5% in no-therapy control groups. About 20 % experience problems in therapy.

ED50: the amount of dose (like the number of sessions in therapy) to get the desired effect in 50 % of the population, the median effective dose.

Law of diminishing returns; the more sessions the less effect of each session.

Clients experience greater effect of long-term programmes than short-term programmes. But if you take the “law of diminishing returns” into account, the short-term programmes are more effective. Most clients experience improvement as coming suddenly, like a light from a blue sky.

Follow-up studies shows that clients generally has “sleeper effect”, they don’t improve or worsens after therapy. Often clients that has had a lot out of therapy, do well at follow-up, while clients that did not get a lot out of therapy, do less well at follow-up.

Often clients have a greater improvement of therapy than psychotropic drugs, even though drugs has a faster effect. In conditions like endogenous depression, that is biological specific, psychotropic drugs will be preferable. Some studies show that a combination of drugs and therapy has the greatest effect, while others show that psychotropic drugs does not improve the effect of therapy, with exception of endogenous depression. Additionally studies show that clients prefer therapy above drugs and there is a greater drop out from treatment with drugs. Therapy has a lower relapse level.

Cost-effectiveness; Therapy is mostly cost-saving for client with in-patient potential, and less effective for clients with affective disorders, who is primarily out-patients.