Therapist-Guided Smartphone-Delivered CBT for MDD

To determine feasibility, we will report rates of and reasons for participant dropout from the trial.

The Client Satisfaction Questionnaire (CSQ) is an 8-item self-report questionnaire which assesses the satisfaction with clinical services received. Each item uses a 4-point Likert scale. Items are summed for a total score ranging from 8 to 32, with higher scores indicating greater satisfaction.

The Credibility/Expectancy Questionnaire (CEQ) is a 6-item, self-report questionnaire. Items 1-3 assess clients' impressions of the treatment credibility; they are scored on Likert scales ranging from 1 to 9 (e.g., from 1='not at all' to 9='very much'). Items are summed for a total score that can range from 3 to 27, where higher scores mean greater treatment credibility.

The Credibility/Expectancy Questionnaire (CEQ) is a 6-item, self-report questionnaire. Items 4-6 are used to assess clients' outcome expectancy. Item 5 is scored on a Likert scale ranging from 1 to 9 (where 1='not at all' to 9='very much'). Items 4 and 6 are scored on a scale from 0% to 100% (in 10-point increments); their scores are then converted linearly on a Likert scale from 1 to 9. Items are summed together for a total outcome expectancy score that can range from 3 to 27, where higher scores mean a higher outcome expectancy.

The Mobile Application Rating Scale user version (uMARS) is a self-report form with 26 items that assess participant's evaluations of various app features. Dimensions of this measure include engagement (5 items), functionality (4 items), aesthetics (3 items), information quality (4 items); other items about app subjectivity quality (4 items) and perceived impact (6 items) are also available but do not contribute to the overall score (and are not reported here). Items are rated on differently worded 5-point Likert scales ranging from 1 (Inadequate) to 5 (Excellent). An overall app rating score can be calculated as the mean score of the first four subscales (engagement, functionality, aesthetics, and information quality; range of 1-5), where higher scores indicate higher overall perceived app quality.

Treatment utilization was assessed with a single question: "On average, how much time (in minutes) do you spend using the app or practicing skills from the app in total, per week?" Answers were collected as number of minutes in integer format, where more time spent on and off the app was interpreted as greater treatment utilization.

The Hamilton Depression Rating Scale (HAM-D) is the gold-standard clinician-administered assessment of depression symptom severity. It contains 21 items that are rated on a mixture of 3- and 5-point Likert scales. The first 17 items are summed for the total score, which can range from 0 to 52. Higher scores indicate greater depression severity.

The Work and Social Adjustment Scale (WSAS) is a self-report measure that assesses impairment in occupational, social, and family areas. The WSAS is a 5-item measure that uses 9-point Likert scales ranging from 0 (no impairment at all) to 8 (very severe impairment). The items are summed for a total score ranging from 0 to 40, where higher scores mean higher functional impairment.

The Quality of Life Enjoyment and Satisfaction Questionnaire-Short Form (Q-LES-Q-SF) is a 16-item, self-report questionnaire that assesses life satisfaction over the past week. Each question is rated on a 5-point Likert scale ranging from 1 (very poor) to 5 (very good). Questions 1-15 are then summed to a total score, and the total score is reported as a percentage maximum possible, such that the final percent score range is 0% to 100%, with higher scores indicating greater quality of life.