The Effectiveness of Interventions for Improving Chronic Pain Symptoms Among People With Mental Illness: A Systematic Review.

Chronic pain (CP) and mental illness (MI) are leading causes of years lived with disability and commonly co-occur. However, it remains unclear if available interventions are effective in improving pain outcomes in patients with co-existing CP and MI. This systematic review synthesised evidence for the effectiveness of interventions to improve pain outcomes for people with comorbid CP and clinically diagnosed MI. Ten electronic databases were searched from inception until May 2023. Randomised controlled trials (RCTs) were included if they evaluated interventions for CP-related outcomes among people with comorbid CP and clinically diagnosed MI. Pain-related and mental health outcomes were reported as primary and secondary outcomes, respectively. 26 RCTs (2,311 participants) were included. Four trials evaluated the effectiveness of cognitive-behavioural therapy, 6 mindfulness-based interventions, 1 interpersonal psychotherapy, 5 body-based interventions, 5 multi-component interventions, and 5 examined pharmacological-based interventions. Overall, there was considerable heterogeneity in sample characteristics and interventions, and included studies were generally of poor quality with insufficient trial details being reported. Despite the inconsistency in results, preliminary evidence suggests interventions demonstrating a positive effect on CP may include cognitive-behavioural therapy for patients with depression (with a small to medium effect size) and multi-component intervention for people with substance use disorders (with a small effect size). Despite the high occurrence/burden of CP and MI, there is a relative paucity of RCTs investigating interventions and none in people with severe MI. More rigorously designed RCTs are needed to further support our findings. PERSPECTIVE: This systematic review presents current evidence evaluating interventions for CP-related and MH outcomes for people with comorbid CP and clinically diagnosed MI. Our findings could potentially help clinicians identify the most effective treatments to manage these symptoms for this vulnerable patient group.