Effectiveness of Acceptance and Commitment Therapy for Chronic Non-Malignant Pain: A Randomized Controlled Trial

Chronic non-malignant pain (CNMP) is associated with significant psychological distress, functional impairment, and reduced quality of life, and pharmacological treatment alone often provides limited relief. This study uses a three-arm, single-blind randomized controlled trial with a pretest-posttest parallel-group design to compare Acceptance and Commitment Therapy (ACT) against Cognitive Behavioral Therapy (CBT, active comparator) and Treatment as Usual (TAU, control).

Sixty adults (aged 18-60) with a physician-confirmed diagnosis of chronic non-malignant musculoskeletal or widespread pain (duration ≥3 months) were enrolled using purposive sampling and randomly allocated to ACT, CBT, or TAU (n=20 per group) using manual simple randomization (fishbowl method). Eligible participants scored ≥4 on the Numerical Rating Scale (pain intensity), ≥4 on the Brief Pain Inventory interference subscale, and ≥20 on the Pain Catastrophizing Scale, and were willing/able to attend all sessions. Individuals with severe psychiatric disorders, severe cognitive/neurological impairment, concurrent structured psychological treatment for pain, or unstable medical conditions were excluded.

The ACT intervention, delivered over 10 weekly sessions using a manual-based protocol adapted for chronic pain, targets the six core processes of the psychological flexibility model: acceptance, cognitive defusion, present-moment awareness, self-as-context, values clarification, and committed action. The CBT intervention, also delivered over 10 weekly sessions, targets maladaptive pain-related cognitions and behaviors through cognitive restructuring, behavioral activation, activity pacing, relaxation training, problem-solving, and coping skills. The TAU group continues routine medical/pharmacological care without structured psychological intervention.

Outcome assessors are blinded to group allocation; participants and therapists could not be blinded given the nature of the interventions. Outcomes are assessed at baseline and post-intervention using the Numerical Rating Scale (pain intensity), Chronic Pain Acceptance Questionnaire (pain acceptance), Brief Pain Inventory (pain interference), Acceptance and Action Questionnaire-II (psychological flexibility), Pain Catastrophizing Scale, Hospital Anxiety and Depression Scale, and WHOQOL-BREF (quality of life). Data collection is complete for the majority of participants; a small number of participants are currently in their final follow-up sessions before post-intervention assessment.

The study aims to (1) evaluate within-group change in ACT and CBT from pretest to posttest across all outcomes; (2) compare ACT versus CBT on post-intervention outcomes, with primary focus on pain acceptance, psychological flexibility, and pain interference; (3) examine whether change in psychological flexibility predicts change in pain interference and catastrophizing across both treatment groups; (4) compare ACT and CBT on anxiety, depression, and quality of life; and (5) compare ACT and CBT against TAU on all outcome measures. Findings are expected to clarify the comparative efficacy and mechanism of action of ACT relative to an established active treatment, contributing evidence for non-pharmacological, mechanism-informed pain management, particularly within an under-studied Pakistani population.

Inclusion criteria

Chronic non-malignant musculoskeletal pain or chronic widespread pain persisting for at least three months, without evidence of malignant pathology Aged between 18 and 60 years Current pain severity of ≥4 on the Numerical Rating Scale (NRS) Pain-related functional interference of ≥4 on the Brief Pain Inventory (BPI) interference subscale Pain catastrophizing score of ≥20 on the Pain Catastrophizing Scale (PCS) Availability and willingness to attend all intervention sessions (10 weekly sessions for either ACT or CBT) Diagnosis medically confirmed by a qualified physician (e.g., orthopedic consultant or pain specialist) prior to inclusion

Exclusion criteria

Presence of severe psychiatric disorders, including but not limited to psychotic disorders, schizophrenia, or bipolar disorder Severe cognitive impairment or neurological disorders that may interfere with understanding or completing study assessments Concurrent participation in other structured psychological interventions for chronic pain (e.g., CBT, ACT) Uncontrolled or unstable medical conditions that may compromise safe participation in the study