Currently, depressive disorders are the fourth disorder worldwide in terms of disease burden, and will be the disorder with the highest disease burden in high-income countries by 2030 [1
]. Depressive disorders are highly prevalent, affecting more than 15% of the general population once in their lives [2
]. Depressive disorders are associated with substantial losses in quality of life in patients and their relatives [3
], with increased mortality rates [4
], with high levels of service use, and with huge economic costs [6
]. Comorbidity is high among depressive disorders, especially with anxiety disorders and alcohol abuse [2
In the last two decades, many studies evaluated self-help interventions as a treatment for depression. Guided self-help can be described as a standardized psychological treatment in which a patient can help himself, with only minimal support from a (professional) therapist. The form in which guided self-help is presented consists of books, videos or computer programs. Several studies have found that guided self-help is effective for the treatment of minor-to-moderate depression [8
], including Internet-based self-help [10
] and meta-analyses have found that the effects of self-help interventions are comparable to those of traditional psychological treatments [11
]. Some support during the Internet intervention has been shown to be important. A meta-analysis of Internet-based cognitive behavior therapy (CBT) for symptoms of depression and anxiety shows that interventions with therapist support had a large mean effect size while interventions without therapist support had a small mean effect size [12
Internet-based self-help is interesting for several reasons. Besides advantages such as low costs and high efficiency, the lack of sufficiently skilled therapists makes self-help approaches attractive [11
]. Furthermore, the Internet offers the possibility of prompt feedback, monitoring and presentation of material on a step-by-step basis [13
]. Another important reason why Internet-based self-help is interesting is that this form of self-help can probably reach many depressed persons who cannot be reached with traditional forms of therapy. Studies carried out in Canada or Europe reported high percentages of undertreatment for adults with depression varying from 36% to 43% [14
]. Many depressed persons who won't go to a professional therapist have objections like 'talking' does not help, lack of willingness to talk to a stranger about personal problems, fear of a stigma [11
]. The low-threshold accessibility of the Internet makes it suitable for offering and receiving help for psychological problems.
Most self-help therapies are developed for treating specific disorders like depression or a specific anxiety disorder. Furthermore, most self-help therapies are based on CBT because face-to-face CBT has proven to be effective [16
] and because its structured format makes it very suitable for self-help purposes. However, it is unknown whether CBT self-help is really more effective than other self-help formats. Problem-solving therapy (PST) may be effective in several problem areas. Face-to-face PST is effective in reducing depression and in several other mental health problems [17
]. As far as we know, there is no study which compares Internet-based CBT with an Internet-based generic intervention like PST, for depression.
However, problem-solving therapies have not been adapted for use through the Internet, so we developed a new, generic method for multiple mental health problems that could be applied through the Internet. As a general framework for the intervention, we used the model developed by Bowman and colleagues [19
], which is called Self-Examination Therapy (SET), and we combined it with cognitive behavioral components and problem-solving procedures. The general idea of SET is that subjects learn to regain control over their problems and lives by (1) determining what really matters to them (2) investing energy only in those problems that are related to what matters (3) thinking less negatively about the problems that are unrelated and (4) accepting those situations that cannot be changed. This method has been found to be effective in several studies in the United States [19
]. In a previous study we have shown the effectiveness of our course in patients with different mental health symptoms [22
]. The comparison between CBT and PST is interesting for another reason. Our PST-based intervention takes only five weeks (CBT in this study takes eight weeks) and may be a worthwhile alternative to other more intensive treatment options.
While there is consensus about the effectiveness of guided self-help for depression, it is still unknown how these interventions work and for whom they work. This holds true for other types of intervention as well. In this study, we examine potential mediating and moderating variables. The main objective of this study is to evaluate the effectiveness of two Internet-based guided self-help treatments with adults reporting elevated depressive symptoms comparing to a waiting list control group. The evaluated self-help treatments are CBT and PST. The secondary objective of this study is to examine potential mediators and moderators. In this article we describe the design of the study.