The present clinical study was aimed at investigating predictors of treatment success, attrition and the extent of treatment needed to achieve clinically significant improvement in spider phobic patients. A total of 103 patients were included in the study after a detailed screening interview. There were four treatment conditions; self-help manual, video, group, and individual treatment, which the patients received in a hierarchical order providing they were not clinically significantly improved after the previous treatment. Pre and post each treatment the patients went through a behavioral approach test and filled in a number of self-report questionnaires. The results showed that 38 patients dropped out during the manual treatment, and 59 fulfilled the treatments to become clinically improved. The patients achieving clinical improvement after the two self-help treatments were significantly predicted, as was the extent of treatment needed. The significant predictors were credibility of the manual treatment and motivation for psychotherapy in general.
Specific phobias are the most common of the anxiety disorders with an estimated lifetime prevalence of 10–15% in the American population (DSM-IV; APA, 1994; Chapman, 1997). Among the specific phobias it seems that phobia of `bugs, mice, snakes, and bats', a category which includes fear of spiders, is the most common in the population with a life-time prevalence of 6.1% (Bourdon et al., 1988; Chapman, 1997). The therapy proven to be most successful for phobias is exposure (e.g. Chambless, 1990; Marks, 1987). Most exposure treatments have been therapist-directed where the therapist usually has weekly sessions with the patient until the problem has been remedied. Recent research has shown that short intensive treatment during a single session produces just as good results as more spaced programs do and could be considered the treatment of choice for specific phobias (Hellström and Öst, 1995; Hellström et al., 1996; Öst, 1996; Öst et al., 1998; Öst et al., 1998; Öst et al., 1997; Öst et al., 1992; Öst et al., 1991). This treatment has also been replicated in spider phobia (Arntz and Lavy, 1993; Götestam, 1994), and there is even earlier research showing that brief treatment of animal phobias is effective (e.g. Bandura et al., 1969).
The efficacy of patient-directed exposure treatment has also been investigated, in search of other methods by which to increase the effectiveness and/or reduce the cost of treatment (Al-Kubaisy et al., 1992; Marks, 1987; Öst et al., 1991). The contact with the therapist has varied from one visit per week to plan new exposure tasks (Mathews et al., 1981), to no contact whatsoever during the treatment period (Ghosh and Marks, 1987; Hellström and Öst, 1995; Öst et al., 1991). The results vary in that some studies found self-directed exposure to be as successful as standard therapist-directed treatment (Ghosh and Marks, 1987), while others found it to do significantly worse (Hellström and Öst, 1995; Öst et al., 1991). However, in the Hellström and Öst (1995) study of spider phobia, the group of patients who used the specific manual at the clinic showed somewhat better effects, especially at the 1-yr follow-up when 63% were clinically improved.
Across our four studies on spider phobia, 89% of the individually treated, 74% of those obtaining group treatment, and 31% of those receiving the self-help manual treatment were clinically significantly improved (according to stringent criteria) at post-treatment. Since a smaller proportion of spider phobics do quite well with a self-help treatment manual it would be of great clinical interest to investigate if it is possible to predict which patients will improve with this treatment, and which will need therapist-directed treatment in order to achieve clinical improvement.
Hellström and Öst (1996) reviewed prediction studies in various anxiety disorders and concluded that it is doubtful if any consistent predictors have been found. Most studies in this area had included too many predictor variables in relation to the number of patients and no cross validation had been done. Thus, the results can very well be considered as chance findings, which rarely are replicated. This was also the outcome of the Hellström and Öst (1996) prediction study (with cross validation) on a large sample of specific phobias. While diastolic blood pressure was a significant predictor in the first sample, it was not found in the second sample. In that sample credibility of the treatments and expectancy to be improved were significant predictors.
Despite this gloomy picture, the aim of the present study was to investigate if there are variables that can predict treatment success and attrition from self-help treatment, as well as the extent of treatment needed to achieve clinically significant improvement. Besides the variables which have been used in previous prediction studies (see Hellström and Öst, 1996, for a review) the present study included motivation for psychotherapy in general. Keijsers (1994) has developed a brief questionnaire which he used in a study of 53 anxiety disorder patients. The results showed that the degree of motivation explained 33% of the treatment outcome, and was the strongest individual predictor.
In order to address this question, a clinical design was used in which a large group of spider phobics all received the self-help manual treatment to begin with. Those who were not sufficiently improved were then offered gradually more therapist-involved treatments until they reached the criteria of improvement decided beforehand.
