Effectiveness of problem solving treatment for patients with undifferentiated somatoform disorder: A cluster randomized controlled trial in primary care

Abstract

Aim To examine the effectiveness of an augmented Problem-Solving Treatment (PST) intervention delivered by mental health nurse practitioners (MHNPs) to patients with undifferentiated somatoform disorder (USD), compared to usual care. Methods We conducted a cluster randomized trial among primary care patients with USD comparing the intervention to usual care. The intervention consisted of six sessions with the MHNP. Primary outcome was physical functioning (RAND-36 physical component summary score). Secondary outcomes were the RAND-36 mental component summary score and the eight subscales; anxiety and depression (Hospital Anxiety and Depression Scale) and somatic symptom severity (Patient Health Questionnaire-15). Outcomes were assessed at baseline, 2, 4 and 12 months. We analyzed data using linear mixed models by intention to treat, and investigated effect modifiers. Results Compared to usual care (n = 87), the intervention group (n = 111) showed an improvement in physical functioning (mean difference 2.24 [95% CI 0.51; 3.97]; p = .011), a decrease in limitations due to physical problems (mean difference 10.82 [95% CI 2.14; 19.49]; p. = 0.015) and in pain (mean difference 5.08 [95% CI 0.58; 9.57]; p = .027), over 12 months. We found no differences for anxiety, depression and somatic symptom severity. Effects were larger and clinically relevant for patients with more recent symptoms and who had fewer physical diseases. Conclusion The augmented PST intervention was effective in improving pain and physical functioning components of patients' health. It was particularly suitable for patients with symptoms that had been present for a limited number of years and with few comorbid physical diseases.