Psychotherapy for chronic major depression and dysthymia: A meta-analysis
Introduction
It is well established that psychological interventions are effective in the treatment of depression. In the past three decades, about 200 controlled and comparative studies have examined the effects of psychological treatments compared to control conditions and to other treatments (Cuijpers, van Straten, Warmerdam, & Andersson, 2008). This large number of studies has shown that psychological treatments have significant effects on depression in adults (Churchill et al., 2001, Cuijpers et al., 2008d). A considerable number of studies has shown that psychological treatments are also effective in specific populations, such as older adults (Cuijpers, van Straten & Smit, 2006), women with postpartum depression (Lumley, Austin, & Mitchell, 2004), and patients with both depression and general medical disorders, including multiple sclerosis (Mohr & Goodkin, 1999), stroke patients (Hackett, Anderson, & House, 2004), and cancer patients (Sheard & McGuire, 1999). Furthermore, several specific types of psychological treatment have been found to be effective. Most research has focused on cognitive behavior therapy, in which restructuring of negative cognitions is the core element (Gloaguen et al., 1998, Churchill et al., 2001). However, several other psychological treatments have also been found to be effective, including interpersonal psychotherapy (de Mello, De Jesus Mari, Bacaltchuk, Verdeli, & Neugebauer, 2005), problem-solving therapy (Malouff et al., 2007, Cuijpers et al., 2007b), behavioral activation (Cuijpers et al., 2007a, Ekers et al., 2008), and psychodynamic therapies (Leichsenring, 2001, Leichsenring and Rabung, 2008). These treatments can be delivered in individual format, group format, or as guided self-help (McDermut, Miller, & Brown, 2001). The effects of psychological treatments are comparable to those of pharmacological treatments (de Maat et al., 2006, Cuijpers et al., 2008b), and combined treatments are more effective than psychological treatment alone (de Maat et al., 2007, Cuijpers et al., 2009) and than pharmacotherapy alone (Friedman et al., 2004, Pampanolla et al., 2004, Cuijpers et al., 2009).
Despite this large body of research, however, very few of the studies on psychological treatments have focused on more chronic forms of depression. It is estimated, however, that 20% of all depressed individuals and up to 47% of the patients treated in mental health care, suffer from a chronic depression (Torpey and Klein, 2008, Arnow and Constantino, 2003). This implies that about 3% of the adult population in Western countries suffers from a chronic depression (Kessler et al., 1994). All depressive disorders have a large impact on quality of life of patients (Ustun et al., 2004, Saarni et al., 2007), and are associated with high levels of service use and enormous economic costs (Berto et al., 2000, Greenberg and Birnbaum, 2005, Smit et al., 2006). Chronic depressive disorders have, however, considerably more adverse impact on quality of life (Wells, Burnam, Rogers, Hays, & Camp, 1992), service use (Howland, 1993), and economic costs (Smit et al., 2006), and more often result in suicide attempts and hospitalization than acute depressive disorders (Torpey and Klein, 2008, Arnow and Constantino, 2003), because they begin early in life in many cases (Keller et al., 2000, Cassano et al., 1992). Moreover, chronic depressive disorders are often lifelong, and are responsible for a considerable proportion of the enormous disease burden associated with depression (Greenberg and Birnbaum, 2005, Keller et al., 2000).
Although the terminology has varied over the years, depressive disorders are considered to be chronic when they last for two years or longer. In the DSM-IV four types of chronic depression are distinguished (Schramm et al., 2008): 1) dysthymia, 2) chronic major depressive disorder (MDD), 3) double depression (MDD superimposed on a dysthymic disorder), and 4) recurrent MDD with incomplete recovery between episodes. Although chronic MDD is more severe than dysthymia, few indications have been found that these two types of depression differ systematically from each other (Torpey and Klein, 2008, Karlsson et al., 2007, McCullough et al., 2003). Prospective research has shown that most patients with dysthymia eventually experience exacerbations for longer or shorter periods of time in which they meet criteria for MDD (Klein, Shankman, & Rose, 2006), which suggests that dysthymia and double depression may be different phases of the same disorder.
Although several meta-analyses have shown that pharmacotherapy is effective in the treatment of chronic depressive disorders and dysthymia (De Lima et al., 1999, Kocsis, 2003), the status of psychological treatments is less clear and sometimes questioned. While several reviews have described the studies examining these psychological treatments (Markowitz, 1994, Torpey and Klein, 2008, Arnow and Constantino, 2003), no meta-analytic study has been conducted, mostly because the number of studies has been considered to be too small for such a study. Some meta-analyses have included small subsamples of studies on dysthymia (Cuijpers et al., 2008a, Cuijpers et al., 2008b, Cuijpers et al., 2008c, Cuijpers et al., 2008d, Imel et al., 2008), suggesting that psychotherapy is less effective than pharmacotherapy in the treatment of dysthymia. However, the evidence is inconclusive, because of the lack of adequately sized samples included in previous meta-analytical research. As will be shown in the present paper, the number of studies examining psychotherapy for chronic depression and dysthymia has grown considerably in the past few years, opening up the possibility to conduct such a meta-analysis that will provide more definite answers.
In light of the increased number of controlled studies we decided to conduct a new meta-analysis in which we collected all studies of psychotherapy for patients with chronic depressive disorders or dysthymia, in which psychotherapy was compared to control conditions, pharmacotherapy and combined treatments of psychotherapy and pharmacotherapy. We expected effect sizes of psychotherapies for chronic depression to be smaller than those of psychotherapies for adult depression in general, because chronic depression is more persistent and a history of previous treatment failure is more common in patients suffering from chronic depression. Furthermore, in concordance with clinical practice for those who are chronically depressed, we expected a combined treatment of psychotherapy and pharmacotherapy to be more effective than either psychotherapy or pharmacotherapy alone.
Section snippets
Identification and selection of studies
A database covering 1036 papers on the psychological treatment of depression was used for the present meta-analysis. This database includes studies on combined treatments and comparisons with pharmacotherapies, and it has been described in detail elsewhere (Cuijpers, van Straten, Andersson, et al., 2008). The database has been used in a series of earlier meta-analyses and more information is available on the Internet (www.evidencebasedpsychotherapies.org). It was developed through a
Characteristics of included studies
Sixteen studies with a total of 2116 patients met our inclusion criteria (689 in the psychological treatment conditions; 167 in the control conditions; 692 in the pharmacotherapy conditions; and 568 in the combined psychological and pharmacological treatment conditions). Selected characteristics of the included studies are presented in Table 1.
Seven studies were aimed at patients with dysthymia (and no major depression; one study in which 15% of the patients also had MDD was categorized in this
Discussion
In this meta-analysis we found that psychotherapy for chronic major depression and dysthymia has a small but significant effect (d = 0.23) on depression when compared to control groups. When psychotherapy was directly compared with pharmacotherapy, it was found that pharmacotherapy was significantly more effective (d = − 0.31). We also found an indication that especially SSRIs were more effective than psychotherapy. However, the studies in which SSRIs were examined were precisely the same studies
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