The DTx group was asked to download and install a smartphone application (WonderLab Harbor) that incorporated Internet-based Cognitive Behavioral Therapy (ICBT), Approach Bias Modification (ApBM), cognitive function training, and Contingency Management (CM). During the 8-week treatment program, the participants in the DTx group were instructed to complete ICBT, cognitive trainings, and ApBM trainings. Reward points (which can be redeemed for cellphone plan credit) were rewarded following completing each task as part of the positive reinforcement following CM principles.

Upon enrollment, TAU participants were informed that they would receive weekly counseling sessions from a social worker for eight weeks. The counseling covered topics including work, family, stress management, and drug craving suppression.

The cognitive behavioral therapy program consisted of eight interactive sessions, each requiring approximately 15 minutes to complete. Each ICBT session includes interactive multimedia modules (videos, pictures, and texts), the contents of which were based on the community reinforcement approach. The ICBT sessions covered the following topics: (1) introduction to digital therapeutics and CBT, (2) recognizing the triggers of craving, (3) coping with craving, (4) refusing skills/assertiveness, (5) problem-solving skills, (6) changing thoughts about drugs, (7) seemingly irrelevant decisions, and (8) HIV risks and prevention.

The cue-induced craving was assessed by showing the participants images related to methamphetamine (methamphetamine crystals, powders, and paraphernalia) on a smartphone and asking them to rate their cravings on a 0-10 visual analog scale (0 being least craved and 10 being most craved).

The cue-induced craving was assessed by showing the participants images related to methamphetamine (methamphetamine crystals, powders, and paraphernalia) on a smartphone and asking them to rate their cravings on a 0-10 visual analog scale (0 being least craved and 10 being most craved).

We use the Meaningless Figure Recognition Test (MFRT) to assess the cognitive function score. This test has eight blocks, and each block has two phases. In the first phase, the participant is presented with a series of meaningless figures one by one for three seconds. The participants were asked to memorize these figures. In the second phase, the previously presented meaningless figures and the same number of the novel meaningless figures are presented on one screen in random order. The participants were asked to recall their memory and click all the previously presented figures within 15 seconds. The correct rate of clicks is used for measuring the cognitive function scores.

We use the Meaningless Figure Recognition Test (MFRT) to assess the cognitive function score. This test has eight blocks, and each block has two phases. In the first phase, the participant is presented with a series of meaningless figures one by one for three seconds. The participants were asked to memorize these figures. In the second phase, the previously presented meaningless figures and the same number of the novel meaningless figures are presented on one screen in random order. The participants were asked to recall their memory and click all the previously presented figures within 15 seconds. The correct rate of clicks is used for measuring the cognitive function scores.

Patient Health Questionaire-9 administered on a smartphone

Patient Health Questionaire-9 administered on a smartphone