Two sessions a week beat one, with the same total number of sessions
Across 70 depression trials with 5,403 patients, the number of sessions had only a small link to the effect, and none after adjustment. Going from one session a week to two, with the total held constant, raised the effect size by g = 0.45.
Reasonable evidence with real limitations. how we score evidence
Caveat on this rating: Metaregression compares across trials, so the frequency effect is observational even though the trials were randomised; confounding by trial design, population or therapy type is possible and the authors flag the finding as needing replication. The g = 0.45 figure is a model estimate, not the result of a trial that assigned frequency.
If you can only afford ten sessions, does it matter whether you take them over ten weeks or twenty? This analysis says it does.
Significant findings
Cuijpers, Huibers, Ebert, Koole and Andersson pooled 70 studies (92 comparisons) with 5,403 patients in which individual psychotherapy for adult depression was compared with a control group such as a waiting list or usual care. They then asked which features of the therapy dose predicted the size of the effect.
Total amount did little. "There was only a small association between number of therapy sessions and effect size, and this association was no longer significant when the analysis adjusted for other characteristics of the studies." Total contact time and overall duration showed no significant association either.
Frequency did a lot. "There was a strong association between number of sessions per week and effect size. An increase from one to two sessions per week increased the effect size with g=0.45, while keeping the total number of treatment sessions constant."
The authors' suggestion follows: "it may be advisable to concentrate psychotherapy sessions within a brief time frame."
The other direction
This is a metaregression: a comparison between trials, not within them. Trials that happened to schedule twice weekly sessions may have differed in other ways. The authors say so: "More research is needed to establish the robustness of this finding." A later randomised trial that assigned people to once or twice weekly sessions is cited on the web page; it is not part of this row.
What this does not show
It does not show that more sessions never help a given person, only that across trials the count of sessions did not predict the average effect once other differences were accounted for.
Worth asking
Would two sessions a week for a month do more than one a week for two months?
Source
How much psychotherapy is needed to treat depression? A metaregression analysis — Cuijpers P, Huibers M, Ebert DD, Koole SL, Andersson G (2013)
Reputable peer-reviewed journal
Read the source: https://doi.org/10.1016/j.jad.2013.02.030
DOI: 10.1016/j.jad.2013.02.030
How this was scored
- Study design
- Meta-analysis of randomised trials
- Funding
- Funding not disclosed
- Published in
- Reputable peer-reviewed journal
- Sample size
- 5,403
- Preregistered
- not recorded
- Conflicts disclosed
- not recorded
- Independent of proponent
- not recorded
- Retracted
- No
Read the full scoring rubric, including what it can't tell you.
Published September 24, 2026.
Questions
How strong is the evidence behind this?
veisund rates this source "moderate evidence". Reasonable evidence with real limitations. It scores 68 out of 100 on our published rubric. One caveat travels with that badge: Metaregression compares across trials, so the frequency effect is observational even though the trials were randomised; confounding by trial design, population or therapy type is possible and the authors flag the finding as needing replication. The g = 0.45 figure is a model estimate, not the result of a trial that assigned frequency. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
How much psychotherapy is needed to treat depression? A metaregression analysis — Cuijpers P, Huibers M, Ebert DD, Koole SL, Andersson G (2013). Published in: Reputable peer-reviewed journal. DOI: 10.1016/j.jad.2013.02.030. The full source is linked on this page so you can read it yourself.
Who paid for this research, and does that matter?
Study design: Meta-analysis of randomised trials. Funding: Funding not disclosed. Independence from the proponent is not recorded. Industry sponsorship is one of the most reliably measured biases in medicine, which is why funding carries real weight in the score rather than sitting in a footnote.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.