The Internet Therapy for Depression Trial

The number of patients with CNCP and suspected major depression who are referred for screening will be recorded. Eligibility rate will be calculated as the number of patients who meet full inclusion criteria divided by the number of patients referred for screening. Number of patients declining referral for screening and reasons for exclusion will be documented. Consent rate will be calculated by dividing the number of patients who consent to undergoing randomization by the number who met full inclusion criteria.

Change in symptoms of depression as measured using the PHQ-9 from baseline to post-intervention. Scores range from 0-27 with higher scores reflecting greater symptoms of depressed mood.

Intervention adherence will be measured using data recorded by Therapist Assisted Online (TAO) program and include: 1) frequency of visits to TAO modules throughout weeks 1 to 8.

Acceptability data will be collected using semi-structured interviews with patients. Open ended questions will be asked to ascertain the following: 1) acceptability of the delivered intervention; 2) perceived value, benefits, harms and unintended consequences of the delivered intervention; 3) perceived need for refinement of the delivered intervention.

Change in pain interference between baseline and post-intervention will be measured using the Brief Pain Inventory - Short Form (BPI-SF). Pain interference is measured s the average degree to which pain impacts seven daily activities (e.g., activity, work, sleep). Scores range from 0 to 10 with higher scores reflecting greater pain-related interference.

Change in depression, anxiety and stress between baseline and post-intervention measured using the Depression, Anxiety Stress Scale - 21 (DASS-21). The DASS is a 21-item Likert scale with questions ranging from 0 (did not apply to me at all) to 3 (applied to me very much or most of the time). The 21 questions are divided into three scales, each comprising of 7 questions: depression, anxiety, and stress. Scores for each subscale range between 0 and 21 with higher scores reflecting greater levels of depression, anxiety, and stress.

Change in pain severity between baseline and post-intervention will be measured using the pain severity composite of the Brief Pain Inventory - Short Form (BPI-SF). Pain severity is measured using the average rating of pain made across the previous 24-hour period (e.g., average pain, worst pain, least pain). Scores range from 0 to 10 with higher scores reflecting greater pain severity.

Change in psychological flexibility between baseline and post-intervention measured using the Multidimensional Psychological Flexibility Inventory (MPFI). The MPFI is a 60-item scale measuring 6 dimensions of psychological flexibility and 6 dimensions of psychological inflexibility as posited by the Hexaflex model. Each item is rated on a 6-point scale ranging from 1 (never or never true) to 6 (always or always true). Measures of psychological flexibility and inflexibility are calculated as the average score across the subscales representing each dimension. Scores range from 1 to 6 with higher scores representing higher levels of the dimensions being assessed.

Change in cognitive behavioural therapy (CBT) skill utilization among patients allocated to the CBT group will be measured among patients assigned to the CBT group using the CBT skills questionnaire. The CBT skills questionnaire is a 16-item self-report measure that assesses the client's frequency and performance of CBT utilization. It is a 5-point Likert scale ranging from 1 ("I don't do this") to 5 ("I always do this"). Higher scores reflect greater utilization of CBT skills.

Change in acceptance of chronic pain will be measured among patients assigned to the acceptance and commitment therapy (ACT) group using the Acceptance and Action Questionnaire (AAQ-II). The AAQ-II is a 7-item self-report measure. Patients rate how true statements are to them on a scale of 1 (never true) to 7 (always true). Score ranges from 7-49, with higher scores reflecting less acceptance and commitment.