Reducing Depressive Symptomatology With a Smartphone App: A Protocol for a Randomized, Placebo-Controlled Clinical Trial

Trial design This study is a randomized, placebo-controlled trial, examining the effects of a CBT intervention in reducing depressive symptomatology for people with moderate symptoms. Participants are randomly assigned to one of the 3 arms of the trial: (1) CBT intervention; (2) placebo intervention (PI); and (3) delayed intervention (wait-list; WL). Major assessments are at baseline, post-treatment, and follow-up 12 weeks later. Participants randomized to the PI and WL trial arms are offered access to the online app upon completion of the study. Participants are blinded to hypotheses and the nature of the placebo intervention, but they are informed they have a 1 in 3 chance of being assigned to the placebo intervention.

Participant timeline Potential participants will be assessed for eligibility through an initial assessment of depressive symptoms. The initial assessment phase consists of administration of the Patient Health Questionnaire-9 (PHQ-9) and a short screening telephone interview. Applicants who do not meet the inclusion criteria are informed via e-mail. They are given a summary score and interpretation for their PHQ-9 score and they are encouraged to discuss their problems with a professional, if necessary. Information on how to reach one - a clinical psychologist or psychotherapist - is also provided. Subsequent assessments consist of all the instruments presented in the Outcome measures section. After the initial assessment, the participants meeting inclusion criteria will be randomly assigned to one of the three conditions: active intervention condition (Group 1), the placebo intervention (Group 2), and the delayed-intervention condition (wait-list) (Group 3).

The participants in the active intervention and active placebo conditions are assessed at pre-intervention (Time 1 - baseline), at mid-intervention (Time 2 - 3 weeks after baseline), at post-intervention (Time 3 - 6 weeks after baseline), and at 3-months post-intervention (Time 4). The participants in the delayed-intervention condition are assessed before the waiting period (Time 1 - baseline), at mid-waiting period (Time 2 - 3 weeks after baseline), and at post-waiting period (Time 3 - 6 weeks after baseline).

Participants assigned to the active intervention condition will be given access to the online application along with explicit instructions regarding the use of all of its sections. Participants will be given 6 weeks to complete the intervention, during which time weekly messages will be sent out to them. Messages include regular assignments designed for a complete and thorough use of the application's courses and exercises, and encourage the review of materials whenever possible. However, participants are free to use the application at their own pace.

Similarly, the participants in the active placebo condition will be given given access to a sham version of the app. During the 6-week intervention period they will be exposed to the same amount of online (i.e., in app messages) and therapist communication as the active intervention participants.