“Is it true that single-session interventions are effective? How is that possible, when even long therapies have modest effects? As a clinician I find this hard to believe.”
The evidence
There is substantial evidence that single-session interventions (SSIs) can be effective in people with mental health problems. Several hundred randomized controlled trials have shown that SSIs, on average, have small but significant effects. These studies have been conducted in children, adolescents and adults, and across several mental health problems, including depression, anxiety, externalizing problems, eating problems, and substance use problems.
How can one session work?
SSIs are probably not equivalent to a full course of psychotherapy. Their effects are typically smaller. Furthermore, the longer-term outcomes are not so clear, and it is quite possible that the effects fade relatively fast.
Their effects may be related to the fact that the association between the number of sessions and the outcome of longer therapies is not linear, and that much of the benefit of therapy occurs early in treatment. SSIs could then generate much of that change in only one session.
In fact, there is no evidence at all that the number of sessions is associated with the outcomes of therapy, at least in depression. In a recent meta-analysis, we examined whether the number of sessions, total contact time, and the length and frequency of sessions (number of sessions per week) were associated with the effects (Ciharova et al., 2024). We found that a higher frequency was associated with better outcomes, while the number of sessions, contact time and length were not.
What makes an SSI different from a short therapy
We should also keep in mind that SSIs are not a regular therapy that simply stops after one session. They typically focus on one specific mechanism — such as behavioral activation, exposure, or problem solving — that can be applied in daily life right away. They are also designed with the assumption that each encounter could be the only encounter.
Why SSIs matter: scalability
The major benefit of SSIs is that they are highly scalable, meaning that they can be applied with relatively few resources and that the threshold to use them is relatively low.
Most people with mental health problems do not have access to evidence-based treatments. More than 80% of people with mental health problems live in low- and middle-income countries, where evidence-based treatments are typically not available at all. But also in high-income countries, many people with mental health problems do not use evidence-based treatments. Less than half of those with a diagnosis of a mental disorder in high-income countries get an evidence-based treatment, and these numbers are even lower in specific high-risk groups, such as older adults, adolescents and young adults, ethnic minorities, and people from groups with lower socioeconomic status.
It is important, therefore, to develop interventions that are scalable. Even when they are somewhat less effective than full treatment, they can still have an enormous impact on mental health.
If these interventions are used by many people, the total impact can be higher than the impact of very effective treatments that are used by only a small, selected group of patients.
SSIs are one of the most promising types of scalable interventions, next to digital tools and, for example, treatments delivered by trained lay counselors. They can be used in lower-income settings as full treatment (it is better to receive an SSI than to receive nothing), but also, for example, for people on waiting lists for treatment, and as an entry point to mental health care.
- For how much therapies actually help, see Does psychotherapy work?
- For why longer is not automatically better, see Are long-term psychodynamic therapies better than brief symptom-focused therapies?
- For whether AI and digital tools can help, see Can I use AI as therapy for mental health problems?
Pim Cuijpers is professor emeritus of clinical psychology and scientific director of Metapsy. He has been involved in more than 1,100 scientific studies, mostly on psychological treatments of mental health problems. This is one of a series of evidence summaries in which Prof. Cuijpers tries to answer questions from patients and clinicians, based on what is known in science about treatments. The knowledge is mostly drawn from collective work of the Metapsy collaboration of at least 15 years. Do you have other questions you would like Prof. Cuijpers to discuss? Feel free to contact us.
Literature
- Ball J, Meiser-Stedman R, Thompson Z, Chiu K. (2026). Self-administered single-session interventions for mental health in young people: a systematic review and meta-analysis. Journal of Child Psychology and Psychiatry. https://doi.org/10.1111/jcpp.70192
- Ciharova M, Karyotaki E, Miguel C, Walsh E, de Ponti N, Amarnath A, … Cuijpers P. (2024). Amount and frequency of psychotherapy as predictors of treatment outcome for adult depression: A meta-regression analysis. Journal of Affective Disorders, 359, 92–99.
- Cuijpers P. (2026). The potential of digital interventions to reduce the disease burden of mental disorders in low- and middle-income countries. American Journal of Psychotherapy, epub ahead of print. https://doi.org/10.1176/appi.psychotherapy.20250035
- Kim J, Ryu N, Chibanda D. (2023). Effectiveness of single-session therapy for adult common mental disorders: a systematic review. BMC Psychology, 11, 373.
- Schleider JL, Zapata JP, Rapoport A, et al. (2025). Single-session interventions for mental health problems and service engagement: umbrella review of systematic reviews and meta-analyses. Annual Review of Clinical Psychology, 21, 279–303.
- Schleider JL, Weisz JR. (2017). Little treatments, promising effects? Meta-analysis of single-session interventions for youth psychiatric problems. Journal of the American Academy of Child & Adolescent Psychiatry, 56(2), 107–115. https://doi.org/10.1016/j.jaac.2016.11.007
