ReviewThe effects of psychotherapies for major depression in adults on remission, recovery and improvement: A meta-analysis
Introduction
More than 350 randomized trials (Cuijpers et al., 2008a) have shown that several psychotherapies are effective in the treatment of major depression in adults, including cognitive behavior therapy (Churchill et al., 2001, Cuijpers et al., 2013a), behavioral activation therapy (Ekers et al., 2008), interpersonal psychotherapy (Cuijpers et al., 2011), problem-solving therapy (Malouff et al., 2007), and possibly non-directive counseling (Cuijpers et al., 2012) and psychodynamic therapies (Leichsenring and Rabung, 2008, Driessen et al., 2010). It has been shown that these therapies result in better acute outcomes when compared to waiting lists, usual care and pill placebo (Cuijpers et al., 2008b), that they are about equally effective as pharmacotherapies for depression (De Maat et al., 2006, Cuijpers et al., 2013b), and that the combination of psychotherapy and pharmacotherapy is more effective than either one alone (De Maat et al., 2007, Cuijpers et al., 2009, Cuijpers et al., 2013c).
But what exactly does it mean that these treatments are effective? Usually the effects of psychotherapies are presented in terms of effect sizes (standardised mean differences at post-treatment), as relative risks (RRs) or as odds ratios (ORs). However, most of these outcomes still do not indicate the likelihood that a person treated for major depression will not meet criteria for depression after treatment, how high the chance is that a patient improves 50% on for example the Hamilton Depression Rating scale (HAM-D; Hamilton, 1960), or how much the average score drops on the HAM-D or Beck Depression Inventory (BDI; Beck et al., 1961).
In many meta-analyses of psychological treatments, standardized mean differences (Cohen׳s d or Hedges’ g) are used to summarize the effects of these treatments. These effect sizes indicate the difference between a treatment and a comparison group in terms of standard deviations. An effect size of 1.0 thus indicates a difference of one standard deviation between the treatment and comparison group. Effect sizes, however, have been criticized for several reasons (Cummings, 2011), including the fact that they may suggest that different treatments are equally effective while they are, in fact, not. They also assume that different scales measuring the same construct are linear transformations of each other (which are often not true). An effect size is also not an indicator of the clinical importance of a treatment. For example, an effect size does not say how many points the average patient improves from baseline to post-treatment on much used depression measures such as the BDI or HAM-D.
In more biomedical meta-analyses dichotomous outcomes are often used as an outcome measure, for example the RR or OR. These indicate the odds or chance of having a better outcome of a therapy (remission, recovery; Frank et al., 1991) compared with the comparison group. But these outcomes are also not very clear in what they exactly mean, because these are relative outcomes that can only be understood in relation to the comparison group. They also do not indicate the proportion of patients that are in remission or recovery after treatment or how many patients do not meet criteria for major depression anymore.
Both effect sizes and dichotomous outcomes can be translated into numbers-needed-to-be-treated (NNTs; Laupacis et al., 1988). Although NNTs are easier to understand by patients, they still indicate the effects in relation to the comparison group and give no absolute effects.
We decided therefore to conduct a meta-analysis of psychological treatments of depression and report their outcomes not in effect sizes, RRs or ORs. Instead, we report the outcomes in absolute terms, including the reduction on scores on much used depression measurement instruments (BDI; HAM-D), how many people have responded (defined as 50% reduction on a depression scale) and are in remission (scoring 6/7 or lower on the HAM-D) after treatment, and how many patients do not meet criteria for MDD anymore.
Section snippets
Identification and selection of studies
We constructed a database of papers on the psychological treatment of depression that has been described in detail elsewhere (Cuijpers et al., 2008a), and that has been used in a series of earlier published meta-analyses (www.evidencebasedpsychotherapies.org). This database has been continuously updated through comprehensive literature searches (from 1966 to January 2013). In these searches, we examined 14,164 abstracts from Pubmed (3638 abstracts), PsycInfo (2824), Embase (4682) and the
Selection and inclusion of studies
Fig. 1 presents a flowchart describing the inclusion process. A total of 92 studies met inclusion criteria. Selected characteristics of these studies are presented in Appendix A.
Characteristics of included studies
In the 92 studies that met inclusion criteria, 181 conditions were examined. Of these 181 conditions, 134 were psychotherapy conditions (70 CBT; 16 IPT; 9 problem-solving therapy; 7 behavioral activation therapy; 8 psychodynamic therapy; 11 non-directive counseling; 13 other types of psychotherapy); 47 control
Discussion
The aim of this meta-analysis was to examine the absolute effects of psychological treatments on the proportion of patients who no longer meet criteria for MDD, response and remission, and the absolute change on the most frequently used outcome measures. We found that the majority of MDD patients who started with psychotherapy no longer met criteria for MDD after treatment (62%). However, in the control conditions also a considerable number of patients no longer met MDD criteria (43%), and even
Role of funding source
No external funding was received for this study.
Conflict of interest
None.
Acknowledgments
None.
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