ABSTRACT
The effects of behavior therapy (i.e., exposure in vivo and response prevention) with obsessive-compulsive (OC) patients have been well established (Marks, 1987; Steketee, 1993; van Balkom et al., 1994). Improvements of exposure in vivo and response prevention have been found to be maintained at up to 3.5 years follow-up (Visser, Hoekstra, & Emmelkamp, 1990). However, there are still a number of OC patients who cannot be treated or who are inadequately treated by behavioral methods only (Foa et al., 1983; Rachman, 1983; Steketee, 1993). Although for some patients treatment effects of behavior therapy may be enhanced by adding drugs like clomipramine or fluvoxamine, there is little evidence that the effects of a combined behavioral and drug treatment are superior to those of behavior therapy on its own (e.g., Kasvikis & Marks, 1988; Marshall & Segal, 1990; Mawson, Marks, & Ramm, 1982; van Balkom, de Haan, van Oppen, Spinhoven, Hoogduin, & van Dyck, 1998; van Balkom et al., 1994). Given the fact that most OC behavior is evoked by thoughts, in recent years some authors have suggested that the role of cognitive factors must be considered (McFall & Wollersheim, 1979; Salkovskis, 1985, 1989).
