ReviewRelapse rates after psychotherapy for depression – stable long-term effects? A meta-analysis☆
Introduction
Depressive disorders represent a significant public health concern due to their prevalence, associated impairment and economic impact (Gustavsson et al., 2011, Kessler et al., 2012, Wittchen et al., 2011). With a lifetime prevalence of 16.6% and a lifetime morbid disk of 29.6% major depressive disorder is the most common mental disorder in the USA (Kessler et al., 2012). Depression can occur as a single-episode, recurrent or chronic disease. Naturalistic prospective long-term studies found recurrence rates that ranged between 35% and 85% over a time span of 15 years, depending on included samples, i.e. population based or clinical (Eaton et al., 2008, Mueller et al., 1999). Chronic courses were seen in about 10–20% of cases (Eaton et al., 2008, Riihimaki et al., 2011, Stegenga et al., 2012).
There is evidence from a large number of randomized controlled trials (RCTs) that psychotherapy is effective in depressive disorders, resulting in moderate to large effect sizes (Barth et al., 2013, Cuijpers et al., 2013a, Cuijpers et al., 2011, Cuijpers et al., 2007, Driessen et al., 2010) that are comparable to those of somatic treatments for physical or mental illnesses or even notably higher (Cuijpers et al., 2013b, Gloaguen et al., 1998, Margraf, 2009). Depending on the studied subgroup of depressive disorders (i.e. dysthymia, chronic depression, depressive episode) the found effect sizes may vary (Cuijpers et al., 2010). It has therefore been suggested that chronic or more severe recurrent forms of depression show a weaker response to purely psychological treatments (Cuijpers et al., 2010) and that in severe depression combined therapy is superior to psychotherapy alone (Thase et al., 1997).
Meta-analytic research also suggested that major types of psychotherapeutic treatments, i.e. CBT, psychodynamic psychotherapy (PDT), interpersonal therapy, and supportive therapy, are equally effective in the treatment of depression (Abbass and Driessen, 2010, Barth et al., 2013, Cuijpers et al., 2013a, Cuijpers et al., 2008, Driessen et al., 2010, Leichsenring, 2001). These results were corroborated by a recent large-scale RCT finding PDT and CBT to be equally effective in the treatment of depression (Driessen et al., 2013). From these results, Thase (2013), p. 954 concluded: “On the basis of these findings, there is no reason to believe that psychodynamic psychotherapy is a less effective treatment of major depressive disorder than CBT.”
However, all of these meta-analytic outcomes refer to short or medium term effectiveness and the number of trials investigating long-term effects of psychotherapy is considerably smaller. The reasons for this might predominantly be methodological as well as economical in nature. Psychotherapy outcome studies with long follow-up durations are more time and cost-intensive than mere pre-post trials or trials with shorter follow-ups. Moreover, attrition rates can be high and confounding variables such as additional or alternative treatment during follow-up are hard to control for and hamper the interpretation of data (Chambless and Ollendick, 2001).
Naturalistic studies found that time spans between depressive episodes can be wide and comprise several months up to many years (Mattisson et al., 2007, Riihimaki et al., 2011, Yiend et al., 2009). Longer follow-up periods therefore provide better estimates of the long-term course of depressive disorders. Also, this kind of data is valuable to assess the long-term effects of common psychotherapeutic treatments, by providing estimates of percentages of patients who do respectively do not benefit from existing treatments and to gain knowledge about the necessity for the development of improved treatment strategies.
There is evidence that about 50% of patients who were recovered by the end of psychotherapeutic treatment suffered a relapse within a time span of two years (Dobson et al., 2008, Emmelkamp, 2013, Gortner et al., 1998, Hollon et al., 2005, Shea et al., 1992, Vittengl et al., 2007). Follow-up studies beyond two years after treatment are scarce.
Additionally, previous findings suggest that psychotherapy (more specifically cognitive therapy, CT) has more enduring effects compared to pharmacotherapy. Gloaguen and colleagues (1998) analyzed eight studies with follow-up durations of at least one and up to two years and found that 29.5% of patients treated with CT relapsed as opposed to 60% of patients who had received medication. In their meta-analysis, Vittengl et al. (2007) studied the effect of CBT on the reduction of relapse in unipolar depression. After completing CBT that started in the acute phase of the depressive disorder, 29% of patients experienced a relapse within the first year and 54% within the second year. These rates were again more favorable than those after antidepressant medication. In sum, long-term effects of psychotherapy for depression are not well studied and largely unknown. Accordingly, Emmelkamp (2013), p. 364 concluded: “Unfortunately, long-term follow-up studies are relatively rare… Given the chronic nature of depression and the high chance of relapse, studies into the long-term effects (beyond 2 years) are needed.”
There is evidence that psychotherapeutic treatment can have enduring effects, however about 50% of patients relapsed within two years, so there seems to be room for improvement. Furthermore, it is not known, how these findings extend to longer follow-up periods of more than two years. Of the 28 trials included by Vittengl et al. (2007) in their meta-analysis of CBT׳s effects on reducing relapse in depression, only three studies comprised a follow-up period of more than two years (Fava et al., 1998, Fava et al., 2004, Paykel et al., 2005). In the meantime, seven years later, several new trials with follow-up periods beyond 24 months have been conducted. Furthermore, the long-term effects of treatments other than CBT for depression were also of interest to us. Thus, our aim was to evaluate long-term effects of psychotherapy trials for depressed patients with follow-up lengths of more than two years.
More specifically, we addressed the following two questions:
- 1.
What is the overall likelihood for a depressive relapse more than two years post-therapy?
- 2.
Is psychotherapy for depression associated with fewer relapses than a non-psychotherapeutic comparison condition in studies with long-term follow-ups of more than 2 years?
Section snippets
Identification of relevant literature
To identify relevant literature, electronic databases PUBMED, PsycINFO and the COCHRANE Central Register of Controlled Trials were searched up to April 15th 2014 for English language articles. Manual searches of reference lists of included studies, relevant meta-analyses as well as database www.evidencebasedpsychotherapies.org (Cuijpers et al., 2014, Cuijpers et al., 2008), an extensive database of trials investigating the effects of psychological treatments of depression, were also performed.
Characteristics of included studies
The conducted literature search yielded 11 RCTs (published between 1998 and 2013) that met selection criteria (Table 2). All in all, long-term follow-up data were available for 966 patients. The number of depressed patients that were included in the follow-ups ranged from 40 (Fava et al., 1998, Fava et al., 2004) to 233 (Conradi et al., 2007). The majority of participants was female (mean 64%), the mean age ranged from 33 (Huber et al., 2013) to 49 years (Paykel et al., 2005). Follow-up times
Discussion
Follow-up research investigating the long-term (i.e. multiannual) effectiveness of psychotherapeutic treatments for mental disorders is very rare. We examined the stability of treatment effects in depressed patients by meta-analyzing outcomes of 11 psychotherapy trials with long-term follow-ups of more than two years. We found that about 40% of patients experienced a relapse (or at least a mild depressive syndrome according to self-reports) by the end of the long-term follow-up assessment that
Role of funding source
This research was supported in part by grants from the Dr. Karl-Wilder-Stiftung. The sponsor had no involvement in study design, in collection, analysis and interpretation of data, in writing the article, and in the decision to submit the article for publication.
Conflict of interest
No conflict declared.
Acknowledgment
None.
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This research was supported in part by grants from the Dr. Karl-Wilder-Stiftung.