Major depressive disorder (MDD) is a mental disorder characterized by a depressed mood, diminished interest or pleasure, sleeping problems and tiredness, and negative thoughts [1
]. The mean one-year-prevalence of depression in European inhabitants between 18 and 65
years old is 6.9% [2
], and 16.2-16.6% of US adults develop a major depressive disorder [3
]. Furthermore, depression causes a high burden worldwide, taking fourth place in a ranking of leading contributors to the burden of diseases in 2000. In 2020, it is estimated that depression will take second place in the ranking for all ages and sexes [5
]. Moreover, depression is the leading cause of years of life lived with disability, in all ages and sexes, accounting for 11.9% of all disability [6
]. Since it appears that persons suffering from mental disorders make more use of health care services [7
], the increasing prevalence of depression leads to an increase in health care costs.
] and Dutch guidelines [9
] suggest treating depression with psychotherapy and/or medication. Psychotherapy follows several kinds of methodologies. For depression, Cognitive (Behavior) Therapy (CBT) and Interpersonal Psychotherapy (IPT) are often applied. CBT originates from behavior therapy and cognitive therapy, and combines elements of both therapies [10
]. IPT was originally developed for treating acute depression by improving the interpersonal functioning with important others [13
]. This study will focus on the effectiveness and efficacy of IPT, since CBT has been subject of many studies up until now, while IPT has only recently become a subject of interest.
As a monotherapy for adults, individual IPT appears to be an effective treatment for depression [18
], and several reviews [21
], and meta-analyses [26
] have been performed on the effectiveness of all kinds of methodologies of psychotherapy. Nevertheless, psychotherapy is a broad concept, and reviews and meta-analyses have often focused on different combinations of psychotherapy for treating depression without comparing one specific sole treatment to another [21
]. Furthermore, although sole individual IPT appears to be effective, few reviews focus on sole individual IPT in adults with MDD as a primary diagnosis. Often, dissimilar study populations are compared with each other, for example adult, adolescent, and elderly patients in one study [23
]. Furthermore, several more types of depression exist: dysthymic disorder or depression with medical conditions, for example, but this review will focus only on MDD. Chronic MDD and postpartum depression (PPD) will be included in this systematic review, for the following reasons. First of all, treatment for patients with chronic and non-chronic depression is equal in terms of content and structure. Therefore, the treatments of these patient groups are comparable. Secondly, the symptoms of both kinds of depression are comparable in terms of severity and content, which makes the patients comparable. Furthermore, women with PPD experience the same kind of symptoms as patients with MDD.
Since comorbidity is very common in patients suffering from depression, and this possibly increases the severity of the depression [36
], this review will focus on MDD as a primary diagnosis with possible comorbidity.
Other factors influencing the results of previously executed systematic reviews include different age groups, in which form the provided IPT is administered, distinct settings, and the time periods during which the studies were executed. IPT is often adjusted for applicability to elderly [45
] or adolescent [46
] depressed patients, or in the form of group IPT [47
]. Therefore, these kinds of treatments may be hard to compare with each other. That is why this review focuses on individual IPT. From here on, when IPT is described in the review, individual IPT is meant, unless described otherwise. Furthermore, the setting in which treatment takes place suggests the depression’s level of severity. It is assumed that inpatients have a more severe depression, which is harder to treat. In addition, inpatient care is often multidisciplinary, which makes it difficult to examine the effects of separate therapies. Research has been conducted on IPT since the 70s, which is why the date limit for this review is set on 1970. This review will give an overview of studies published between January 1970 and August 2012, with a focus on sole IPT administered to adults. Since some therapies have an effect relatively quickly, we did not apply a minimum for duration of a therapy.
With all of the above in mind, the aim of this study is to give an overview of recent literature describing the effectiveness and efficacy of sole individual IPT in comparison with standardized forms of treatment for treating patients with MDD as a primary diagnosis. The following research question has been formulated: Is individual interpersonal psychotherapy more preferable in comparison with other standardized forms of treatment for treating adult outpatients with a primary diagnosis of major depressive disorder?
In order to answer this question, a systematic review will be performed on RCTs and C-RCTs comparing the effectiveness (the outcome of a new treatment compared to other kinds of treatment(s), usually in a clinical setting) or efficacy (the outcome of treatments in homogeneous patient groups, usually in an experimental setting) [48
] of individual sole IPT with other standardized forms of treatment, for treating adult outpatients with MDD as a primary diagnosis.