Can you guess what the most commonly attended number of therapy sessions is? It’s one session. With this in mind, single-session interventions (SSIs) aim to maximise a one-off interaction with mental health support, without assuming that the person will return or complete another session. They are described as “structured programs that intentionally involve only one visit or encounter with a clinic, provider, or program” (Schleider et al. 2020), and have previously been blogged about on The Mental Elf by Dr Maria Loades and Georgia Kemp.
While SSIs have been around for several decades, interest in them has skyrocketed over the past 10 years. This is likely due to the appeal of a low-cost, scalable way of reaching more people in need (particularly if they are delivered online) at a time when many spend months on waiting lists, which only happens once they have met thresholds for accessing formal mental health support in the first place (Loades & Schleider, 2023).
Due to the increase in clinical trials evaluating the benefits of SSIs for mental health problems, researchers from the Lab for Scalable Mental Health in the US sought to bring them all together and evaluate their effectiveness in an umbrella review (i.e., a systematic review of systematic reviews).
Single-session interventions aim to maximise the effectiveness of a one-off therapeutic intervention. But do they actually achieve this?
Methods
Schleider et al. (2025) combed through the literature to find systematic reviews (SRs) measuring the effectiveness of SSIs (defined as interventions that intentionally involved just one visit or encounter with a clinic, provider, or program) through clinical trials for a wide range of mental health problems, substance use, or engagement with mental health services. They followed the standard procedure for umbrella reviews, and systematically searched well known databases (e.g., MEDLINE, PsycINFO) and thesis platforms, as well as hand-searching for any ongoing reviews.
The inclusion of meta-analyses (a statistical way of combining findings from different studies) was optional, but narrative reviews (those that only described the findings without combining them in a standardised way) were excluded. Other exclusion criteria included SSIs targeting motivation or readiness to seek treatment, SSIs that used pharmacotherapy, and SRs focused on Critical Incident Stress Debriefing for posttraumatic stress.
The search resulted in 1,391 papers, of which the authors selected 63 as suitable for full-text review, and ended up including 24 systematic reviews that matched all criteria they were looking for.
Finally, a commonly used tool (AMSTAR 2) to measure the accuracy and transparency of each included systematic review was used, to assess the scientific rigour with which each review was conducted.
Results
Study characteristics and overall effects
- 24 systematic reviews containing 415 individual clinical trials were included in the umbrella review. These trials involved approximately 40,629 participants with ages ranging from five to 90 years old.
- 62% of the systematic reviews were published between 2019 and 2024, showing a sharp increase in newly published clinical trials evaluating the benefits of SSIs in recent years.
- Of the 24 included systematic reviews, 20 found overall benefits of SSIs on a range of clinical outcomes. Only two systematic reviews focused on SSIs to improve engagement with mental health services, highlighting a lack of evidence in this area.
- 12 of these reviews included a meta-analysis. Based on these, the authors found a small, positive overall effect of SSIs across various mental health problems and age groups, compared to control participants in these studies (g = −0.25).
- To put this into perspective, recent umbrella reviews evaluating multi-session psychotherapies across all mental health problems found an overall effect of g = -0.34, which is also considered small.
Which clinical outcomes benefit from SSIs?
- Eight of the 10 systematic reviews evaluating SSIs for substance use found overall benefits on problematic alcohol use and smoking cessation, both amongst young people and adults. Most SSIs used motivational interviewing as their ‘active ingredient’.
- Eight of nine systematic reviews focusing on anxiety found overall benefits. SSIs targeted specific phobias and generalised anxiety using cognitive behaviour therapy (CBT) techniques, graded exposure for specific phobias, and even exercise such as yoga as the ‘active ingredient’.
- Five of six systematic reviews focusing on depression found overall benefits, with SSIs using CBT components or behavioural activation (helping people do more of what they enjoy).
- One of two systematic reviews assessing SSIs for eating problems, including dieting, body mass, thin ideal internalisation, and body dissatisfaction, found overall benefits.
Does mode of delivery have an impact?
- Each of the four systematic reviews on self-guided SSIs for young people reported overall benefits for at least one of the mental health outcomes measured.
- However, most studies focused on human-delivered SSIs (e.g., with a therapist), with 14 of 16 reviews finding overall benefits of this type of SSI compared to control groups.
How long do the benefits last?
- It is difficult to tell because the follow-up times varied greatly among individual studies in the included systematic reviews. They ranged from measuring outcomes immediately after the SSI to two years post-SSI.
Which is best – single-session or multi-session interventions?
- Four meta-analyses compared SSIs with multi-session interventions, with mixed findings. Two meta-analyses found no significant differences, one found a single-session motivational interviewing intervention to be more beneficial than a multi-session programme, whereas one found multiple sessions to be more helpful.
- This makes it tricky to conclude exactly how SSI perform compared to traditional multi-session therapy.
This umbrella review identified 24 eligible systematic reviews, combining data from 415 individual trials. Overall, 83% of the reviews found beneficial effects of single-session interventions for at least one clinical outcome.
Conclusions
Based on the 24 included systematic reviews, this umbrella review found an overall small-to-moderate effect of SSIs on a range of mental health problems, including substance use, depression, anxiety, and engagement with mental health services. This effect is slightly lower that the effects usually found for traditional, multi-session psychotherapies.
Despite the smaller effect, given that SSIs are a low-cost option with the potential to reach more people at a quicker rate, Schleider et al. (2025) concluded that SSIs can be helpful to people with various mental health problems. Importantly, they do not suggest that SSIs should replace multi-session therapy; rather, they recommend that SSIs should be a complementary offer to traditional or more high-intensity forms of support.
Single-session interventions should not replace traditional, multi-session support; instead, they can complement what is already on offer.
Strengths and limitations
This is the first umbrella review bringing together systematic reviews evaluating SSIs for mental health problems, meaning it fills a crucial gap in the literature and aids clinical recommendations to be made on the implementation of SSIs. The authors thoroughly searched the literature, including unpublished reviews, to ensure the searches are as up to date as possible. They assessed the quality of individual reviews and commented on their transparency and strengths and limitations, increasing the transparency of the umbrella review itself. However, the authors do point out that many individual systematic reviews did not report pre-registration, meaning it is possible that some of the outcomes were selectively or not transparently reported.
While the authors discussed the limitations of the included reviews, they did not comment on any limitations of the umbrella review itself. However, there are some limitations, including the fact that not all the reviews included just randomised controlled trials, which are considered the ‘gold standard’ for measuring the effectiveness of psychosocial interventions. As some reviews contained non-randomised trials, it is not clear how the control groups in those studies were set up and whether certain participants (e.g., volunteers for the intervention condition), were more likely to share some characteristics, such as motivation or mental health symptoms. This can make it difficult to draw conclusions about the effectiveness of the intervention itself versus other shared factors among the participants.
SSI duration varied greatly between studies and therefore assessing them together means we cannot tell whether session length makes a difference to the effectiveness. Similarly, SSI effectiveness was measured at various timepoints after the intervention, so it is not clear how long-lasting the benefits are.
The main strength of this umbrella review is in its thorough and transparent reporting. However, the inclusion of non-randomised trials could introduce bias to the findings.
Implications for practice
This umbrella review significantly contributes to the literature on SSIs by being the first to synthesise available systematic reviews assessing their benefits. As shown in this umbrella review, the number of developed and tested SSIs has been continuously growing, and there is hope that they can supplement current mental health service provision (Loades & Schleider, 2023). As such, it’s important for clinicians and researchers to be able to review and draw on evidence-based recommendations and potential benefits of SSIs, particularly those from meta-analyses as they are considered the strongest type of evidence for intervention effectiveness in the research world.
I understand that there can be scepticism around SSIs, e.g.:
- How can a one-off intervention possibly help someone in need?
- Will this replace 12-week courses of therapy and the hard work of therapists?
- What about managing risk?
I think this umbrella review is transparent about what it can tell us about SSIs. While the evidence here does show their potential clinical benefits, particularly as some of the individual reviews found that multi-session therapies did not outperform SSIs, the authors also highlight many areas that still need to be investigated in order to improve the implementation and benefits of SSIs. Follow-up times vary greatly, making it difficult to draw conclusions on how long-lasting the effects are. Even if the SSIs are useful, without knowing how and to what extent they can be implemented in real life, their benefits will be limited, so more research is needed on this.
Personally, when I think of the promise of SSIs, I think of a teen who is dealing with a specific phobia and who receives a one-off session while on a waiting list for multi-session therapy. The one-off session teaches them some basic skills and how graded exposure therapy works, giving them a sense of agency and motivation while they wait. I think of a young adult dealing with mild low mood symptoms, but who isn’t quite sure what’s happening yet. They come across a self-guided, online SSI teaching them behavioural activation skills. This one-off session helps them understand their struggles and put it into words. This empowers them to seek further help while practising behavioural activation exercises as they explore mental health support in their area.
Despite my optimism, I would echo what the authors said – SSIs are most likely to complement, rather than replace multi-session support provision. There are people for whom one or several one-off interventions may be enough, and for others, they will need further support. But at a time when people are struggling to access any type of mental health help or support, SSIs may be an additional tool under the belt of mental health support systems.
For some people, SSIs may be able to provide them with the support that they need; for others, SSIs may provide a stepping stone to further support. Either way, SSIs seem like a beneficial tool in the toolbox.
Statement of interests
NK was not involved in the study summarised above, but she is a PhD researcher developing a single-session intervention. Her research group collaborates with some of the authors of the study in this blog on developing and adapting SSIs for young people in the UK.
Links
Primary paper
Schleider, J. L., Zapata, J. P., Rapoport, A., Wescott, A., Ghosh, A., Kaveladze, B., … & Ahuvia, I. L. (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.
Other references
Loades, M., & Kemp, G. (2022). Just one shot at it: single session interventions for adolescent depression. The Mental Elf.
Loades, M. E., & Schleider, J. L. (2023). Technology Matters: Online, self‐help single session interventions could expand current provision, improving early access to help for young people with depression symptoms, including minority groups. Child and Adolescent Mental Health, 28(4), 559-561
Schleider, J. L., Dobias, M., Sung, J., Mumper, E., & Mullarkey, M. C. (2020). Acceptability and utility of an open-access, online single-session intervention platform for adolescent mental health. JMIR Mental Health, 7(6).