“All life is problem solving” suggested the philosopher Karl Popper (Popper & Camiller, 2013).

In mental health, we might say, “all psychotherapy is problem solving.” For example, problem solving is part and parcel of many psychotherapies for depression, including cognitive behavioural therapy (CBT), interpersonal psychotherapy (IPT), family therapy, and dialectical behaviour therapy (DBT).

Problem solving therapy (PST) is also a therapeutic approach in its own right with roots in Social Learning Theory that was developed by Thomas D’Zurilla and Marvin Goldfried in the 1970s (D’Zurilla & Goldfried, 1971).

Problem solving training typically builds self-efficacy and teaches rational problem solving skills, based on the idea that effective and rational problem solving protects from the negative effects of chronic or sudden stress, while ineffective problem solving (e.g., avoiding problems, leaving them for others to solve, or jumping on the first solution that comes to mind) does not. Problem-solving training can be brief (i.e., fewer than 10 sessions) and be delivered by trained clinicians, general practitioners, lay counsellors, or online. It is a versatile treatment ingredient that deserves greater scrutiny as a means to tackle depression.

In this blog, I review findings from an updated meta-analysis published in 2018 by Pim Cuijpers and colleagues (Cuijpers et al., 2018). The meta-analysis assessed the effectiveness of stand-alone PST for adults with depression, compared with control conditions and with other evidence-based therapies.

I also talk about my own recent Wellcome Trust-funded review of problem solving for young people with depression.

Methods

Randomised controlled trials were retrieved from an existing database that was compiled through systematic searches in PubMed, PsycInfo, Embase and the Cochrane Library, and databases specifically cataloguing trials from lower- and middle-income countries. For inclusion, studies had to be randomised controlled trials (RCTs) comparing problem solving therapy (PST) for adult depression (established via a diagnostic interview or above-threshold self-report score) with a control group (e.g., waitlist, treatment as usual, placebo, etc.) or with another active treatment. Maintenance studies or those using inpatient samples were excluded. RCTs for other types of psychotherapy for depression were also retrieved to compare their effectiveness to that of PST. Two reviewers independently screened abstracts and full texts.

All included studies underwent a risk of bias assessment using the Cochrane Collaboration’s assessment tool, and reviewers coded suspected “researcher allegiance” in favour of PST (e.g., where PST was mentioned as the principal intervention to be tested in a paper’s introduction). A random effects meta-analysis assessed the difference in depression scores between intervention and control groups post treatment, using Hedge’s g and a correction for small sample bias. Subgroup and multivariate meta-regression analysis aimed to identify causes of heterogeneity, and publication bias was also examined.

Results

The meta-analysis considered 30 PST trials and 264 trials of other therapies for comparison. Close to two thirds of PST trials had been done in North America, one third in Europe, and one trial in Africa. There was considerable risk of bias in most PST trials, with only seven out of 30 meeting all Cochrane criteria of high quality.

Key findings

• PST versus control group (27 comparisons): there was a large and significant overall effect in favour of PST (g = 0.79; 95% CI: 0.57 to 1.01), but heterogeneity was high (I² = 84), and there was a strong indication of publication bias:
  • When considering only studies with low risk of bias, the effect size was smaller (g = 0.34; 95% CI: 0.22 to 0.46), and heterogeneity was low (I² = 32).
  • Several study characteristics were significantly related to effect size in a subgroup analysis (see Table 1 below), but only low risk of bias remained significant in a multivariate meta-regression (associated with smaller effect sizes).
• PST versus another type of psychotherapy (12 direct comparisons): PST was slightly superior (g = 0.18; 95% CI: 0.01 to 0.35), with low heterogeneity (I² = 27), but there was researcher allegiance pro PST in most studies.
• PST versus antidepressants (6 comparisons): No statistically significant effect was found (g = 0.09; 95% CI: -0.13 to 0.30).

When comparing the effect size for PST with those achieved by other psychotherapies (compared with control groups), there was no statistically significant difference in effectiveness.

Table 1. Findings about possible causes of heterogeneity

Study characteristic	Initial subgroup analysis	Subgroup analysis after removing studies with very high effect sizes to avoid distortion	Multivariate regression analysis—full model	Multivariate regression analysis—parsimonious model
Participants recruited from the community (vs. clinical settings)	✔️	✔️
Group-based PST (vs. individual)	✔️	✔️
Done in North America (vs. Europe or Africa)	✔️
Using a wait-list control (vs. treatment as usual or other comparison group)	✔️	✔️
Low risk of bias (vs. high risk)	✔️	✔️		✔️
Target group (adults; older adults)
Diagnosis (diagnosed disorder or above cut-off)
Type of PST (extended, brief, self-directed)

Conclusions

The authors concluded that despite some limitations, this meta-analysis showed that:

PST is probably an effective treatment of [adult] depression, with effect sizes that are small, but comparable to those found for other psychological treatments of depression (p. 35).

Strengths and limitations

The authors provide a thorough and systematic approach to assessing the evidence, controlling for possible sources of bias (e.g., publication bias, researcher allegiance, distorting influence of very high effect sizes), and investigating causes of heterogeneity.

The sample of studies was too small to examine the influence of factors such as treatment length or delivery format on PST effectiveness, with a lack of high-quality studies (k = 9) in particular. Publication bias, and researcher allegiance in over half of the included studies were additional barriers to drawing credible conclusions. The authors could have further enhanced the strength of their review by using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system to appraise the overall quality of the evidence and of the clinical recommendations that can be made on their basis (Guyatt et al., 2008).

Implications for practice

Problem solving therapy is not currently recommended as a stand-alone treatment for adult depression by the NICE guidelines, but this meta-analysis found it could be offered as an alternative to CBT or IPT, with similar expected benefits.

Problem solving training for young people with depression: our Active Ingredients review

We were inspired by this finding from Cuijpers et al (2018) that problem solving therapy (PST) is as effective as evidence-based therapy packages (including CBT), because problem solving is one of the coping skills that youth most frequently use in their daily lives (Ng et al., 2016). Learning coping and self-management skills is also a key desired outcome of depression treatment in the eyes of youth with lived experience (Krause et al., 2020a; Krause et al., 2020b). This got us interested in looking at problem-solving as an active ingredient of treatment for youth depression.

We conducted a scoping review that considered four clinical trials of stand-alone PST for youth depression; four secondary analyses of trial data looking at problem solving as a predictor, moderator, or mediator of treatment response; and 24 clinical practice guidelines for youth depression.

Our findings suggest that there is currently no strong evidence in favour of PST as a stand-alone treatment for reducing youth depression symptoms. Stand-alone PST may be beneficial for youth who face stress from challenging events or daily hassles and who struggle with problem solving, but whose mental health difficulties are relatively mild. In turn, the current evidence base suggests that youth who struggle with low mood and other depression symptoms may require broader psychotherapeutic support to recover from their depression. More high-quality research is needed to investigate the effective of problem-solving training for youth.

We had the chance of having two youth advisors work with us as co-researchers. They consulted a larger panel of youth research advisors at the Centre for Addiction and Mental Health in Toronto, Ontario to help us contextualize our review findings. From our youth advisors we learned that in order to be meaningful, problem-solving training should be:

• youth-driven (with youth rather than therapists defining the problem)
• strengths-based (avoiding deficit-focused language)
• comprehensive (by considering the root causes of superficial problems) and
• personalised (by embracing people’s individual problem solving styles).

In order to be acceptable to youth, problem-solving training needs to be youth-driven, strengths-based, comprehensive, and personalised.

Statement of interests

Karolin’s team at the Cundill Centre for Child and Youth Depression (Centre for Addiction and Mental Health) received funding through the Wellcome Trust Mental Health Priority Area ‘Active Ingredients’ commission to conduct their review of problem solving training as an active ingredient for treating youth depression.

Links

Primary paper

Cuijpers, P., de Wit, L., Kleiboer, A., Karyotaki, E., & Ebert, D. D. (2018). Problem-solving therapy for adult depression: An updated meta-analysis. European Psychiatry, 48, 27–37. https://doi.org/10.1016/j.eurpsy.2017.11.006

Other references

Cuijpers, P., de Wit, L., Kleiboer, A., Karyotaki, E., & Ebert, D. D. (2018). Problem-solving therapy for adult depression: An updated meta-analysis. European Psychiatry, 48, 27–37. https://doi.org/10.1016/j.eurpsy.2017.11.006

D’Zurilla, T. J., & Goldfried, M. R. (1971). Problem solving and behaviour modification. Journal of Abnormal Psychology, 78(1), 107–126. https://doi.org/10.1037/h0031360

Guyatt, G. H., Oxman, A. D., Vist, G. E., Kunz, R., Falck-Ytter, Y., Alonso-Coello, P., & Schünemann, H. J. (2008). GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ, 336(7650), 924–926. https://doi.org/10.1136/bmj.39489.470347.AD

Krause, K., Midgley, N., Edbrooke-Childs, J., & Wolpert, M. (2020a). A comprehensive mapping of outcomes following psychotherapy for adolescent depression: The perspectives of young people, their parents and therapists. European Child & Adolescent Psychiatry. https://doi.org/10.1007/s00787-020-01648-8

Krause, K. R., Edbrooke-Childs, J., Bear, H. A., Calderón, A., & Wolpert, M. (2020b). What Treatment Outcomes Matter Most? A Q-study of Outcome Priority Profiles Among Youth with Lived Experience of Depression. MedRxiv, 2020.10.12.20210468. https://doi.org/10.1101/2020.10.12.20210468

Ng, M. Y., Eckshtain, D., & Weisz, J. R. (2016). Assessing Fit Between Evidence-Based Psychotherapies for Youth Depression and Real-Life Coping in Early Adolescence. Journal of Clinical Child and Adolescent Psychology, 45(6), 732–748. https://doi.org/10.1080/15374416.2015.1041591

Popper, K., & Camiller, P. (2013). All life is problem solving. In All Life is Problem Solving. Psychology Press. https://doi.org/10.4324/9780203431900