Predictors of response to psychological treatment in somatoform disorder and somatic symptom disorder: A meta-analysis

Abstract

Aims: Somatoform disorder and somatic symptom disorder are associated with substantial psychosocial and functional impairment. Meta-analysis can clarify whether this group of disorders tends to be difficult to treat and whether effects of therapy depend on specific variables. The main aim of the present meta-analysis was to examine whether type of intervention and type of outcome variable predicted response to treatment. Methods: Included were studies evaluating a psychological intervention given to patients diagnosed with somatoform disorder or somatic symptom disorder. Of 2,655 initially identified records, 22 studies were eligible for quantitative analysis, involving 3,160 patients. Outcome domains were somatic symptoms, psycho-behavioral features (e.g., psychopathology) and illness consequences (e.g., mental and physical well-being and functioning). Results: An overall medium-to-large pre-post effect size across 27 intervention conditions (d = 0.77) and a medium pre-post effect size across 10 control conditions (d = 0.49) was obtained. Psychological interventions were significantly superior to control conditions for illness consequences but not for somatic symptoms or psycho-behavioral features. Pre-post effect sizes for cognitive-behavioral therapy (CBT) did not significantly differ from those of other psychological interventions. Longer symptom duration, younger age and lower methodological quality predicted larger effect sizes. Conclusion: Overall, the present findings suggest that psychological interventions are effective in improving illness consequences but may not yield larger amounts of change when compared to control conditions in terms of symptoms or psychopathology. Effects of CBT did not prove superior to effects of other psychological interventions. Relatively modest effects of treatment and the difficulty of identifying modifiable predictors of treatment effects, such as type of treatment, provide support for previous suggestions in the literature that somatoform disorder is difficult to treat.