Ninety five percent of people who improved in NHS therapy had done so within 14 sessions
In 102,206 patients across 16 NHS services, 95% of responders had improved within 7 sessions of low intensity CBT or 14 sessions of high intensity CBT. Social anxiety, PTSD and OCD ran longer, 6 to 16 sessions.
Reasonable evidence with real limitations. how we score evidence
Caveat on this rating: A routine-care data set, not a trial: patients were not assigned a number of sessions, and people who dropped out early may have been counted differently from those with planned endings. The 14-session figure is the point by which most responders had responded, not a ceiling on who can respond. Two symptom questionnaires define response; functioning and quality of life were not measured here.
This is the largest single data set on the question, and it was collected from ordinary public services, not a university clinic.
Significant findings
Robinson, Kellett and Delgadillo analysed records from 102,206 patients across 16 English NHS stepped care services. Everyone had case level depression or anxiety symptoms and received low intensity CBT (guided self help), high intensity CBT (a course of sessions with a therapist), or both. A responder was someone whose scores on the PHQ-9 or GAD-7 showed reliable and clinically significant improvement by the end of treatment.
The authors then asked, session by session, how long it took to find 50%, 75% and 95% of the people who were going to respond. "Most responders (95%) attained RCSI within 7 sessions of LiCBT and 14 sessions of HiCBT."
Not every problem fit the same window. Patients with social anxiety disorder, post traumatic stress disorder and obsessive compulsive disorder "required HiCBT and lengthier treatments (6-16 sessions) to maximize improvement."
The authors propose using the 50% and 95% points as the lower and upper edge of an adequate dose, to time a progress review rather than to set a limit.
The other direction
Responders are the people who got better. The study says when they got better; it does not say that a person who has not responded by session 14 will not. Some conditions needed the longer end, and the study measured two questionnaires, not everything a person might want from therapy.
What this does not show
It does not compare people who stopped at 14 sessions with people who continued. It is a description of when response arrived across a very large group.
Worth asking
If I have not moved by session eight or so, what do we do differently?
Source
Dose-response patterns in low and high intensity cognitive behavioral therapy for common mental health problems — Robinson L, Kellett S, Delgadillo J (2020)
Reputable peer-reviewed journal
Read the source: https://doi.org/10.1002/da.22999
DOI: 10.1002/da.22999
How this was scored
- Study design
- Cohort study
- Funding
- Funding not disclosed
- Published in
- Reputable peer-reviewed journal
- Sample size
- 102,206
- 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 55 out of 100 on our published rubric. One caveat travels with that badge: A routine-care data set, not a trial: patients were not assigned a number of sessions, and people who dropped out early may have been counted differently from those with planned endings. The 14-session figure is the point by which most responders had responded, not a ceiling on who can respond. Two symptom questionnaires define response; functioning and quality of life were not measured here. 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?
Dose-response patterns in low and high intensity cognitive behavioral therapy for common mental health problems — Robinson L, Kellett S, Delgadillo J (2020). Published in: Reputable peer-reviewed journal. DOI: 10.1002/da.22999. 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: Cohort study. 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.