The future of psychotherapy research: stop the waste and focus on issues that matter.

It is well-established that psychotherapies can effectively treat depression. In the past four decades, more than 400 randomized controlled trials have been conducted (Cuijpers, 2015), showing that different types of psychotherapy are effective (Barth et al. 2013), that the effects do not or only marginally differ from each other, that they are comparable with those of antidepressants, and that combined treatment is more effective than psychotherapy or medication alone (Cuijpers, 2014). However, psychotherapies are probably less effective in chronic depression and dysthymia, when patients have comorbid alcohol problems, and in subthreshold depression, although in these patients therapies can prevent the onset of full-blown major depressive disorders (Cuijpers et al. 2014). The two Editorials in this issue give interesting perspectives onwherewearewith researchon these therapies andwhat should happen in the future (Hollon, 2015; Solomonov & Barber, 2015). The first thing that stands out is that both agree that although psychotherapies are effective, there is still considerable room for improvement. The Editorials point at the problem that the effects of psychotherapy have been overestimated because of publication bias, but also that the longer term effects of psychotherapies are not well known, except maybe for cognitive-behavioural therapy where longer-term effects have been shown (Karyotaki et al. 2014) in several trials. The small effects of psychotherapies and treatments in general in chronic and treatment-resistant depression (Cuijpers et al. 2010d) and the high relapse rates after successful recovery (Vittengl et al. 2007) are also important problems. I want to underscore that although therapies are effective, there is still much room for improvement. The effect sizes found for treatments for mental disorders do not differ very much from those in general medical disorders (Leucht et al. 2012), but still it is estimated that current treatments cannot take away more than one-third of the disease burden of depression, and then only in optimal conditions (Andrews et al. 2004). And then there is the problem that more than 40% of the patients do not or only partially respond to treatment and less than one-third of the patients are completely recovered after treatment (Hollon et al. 2002). And after successful response the relapse rates are estimated to be 50% after 2 years and up to 80% after 5 years (Vittengl et al. 2007). These problems are in addition to the problem that much of the earlier research has considerably overestimated the effects of acute treatments of depression, not only because of publication bias, but also because of the low quality of many trials in the field (Cuijpers et al. 2010c) and probably researcher allegiance (Munder et al. 2013). Both articles give indications for how future research can contribute to a further reduction of the disease burden. In addition to that, however, I would like to stress that there is also much research that is not needed anymore in the future. In the broader biomedical field it is estimated that about 85% of research is wasted, because of irrelevant questions, inappropriate designs and methods, and biased reporting (Chalmers & Glasziou, 2009). There is no reason to assume that this is very different in randomised trials of psychotherapies for depression. We found earlier that of 115 trials in this field only 11 met all nine generally accepted quality criteria, and that the effects of these 11 studies were considerably smaller than those of lower-quality studies (Cuijpers et al. 2010c). We also found that adjusting for unpublished trials reduces the effect size of psychotherapies with more than one-third (Cuijpers et al. 2010b), and reporting in these trials also is often biased (Flint et al. 2014). Address for correspondence: Professor P. Cuijpers, Department of Clinical Psychology, VU University Amsterdam, Van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands. (Email: [email protected]) Epidemiology and Psychiatric Sciences (2016), 25, 291–294. © Cambridge University Press 2015 doi:10.1017/S2045796015000785 EDITORIALS IN THIS ISSUE