"Thought Viruses": A Mental Self-Help App

OBJECTIVES: Develop, deploy, and evaluate the health economics of a low-threshold self-help app for mild to moderate anxiety and depression.

METHODS: The TANKEVIRUS (Thought Virus) app, available for free on Android and iOS in Norway, is funded by the Norwegian Directorate of Health. Upon entry, users consent to participate and store anonymous data. The app features stages (evaluations, introduction, intervention) that unlock progressively. Users measure their mental health using the 4-item Patient Health Questionnaire (PHQ-4) and 8 item somatic symptom scale (SSS-8) at the start, completion (around 21 days), and at 3 and 6 months, alongside a general health Visual Analog Scale, age, and gender. Users are offered three 10-minute introductory videos based on cognitive behavioral therapy (CBT) and, for the next 20 days, receive daily 1-2 minute videos offering tips and tasks to manage negative thoughts. Push notifications improve adherence. Self-reported anxiety and depression (PHQ-4) were compared before and after use, with scores mapped to EQ-5D utilities to estimate cost per QALY.

RESULTS: Between Q1 2022 and Q1 2024, 109,000 unique users (77% female) initiated the app; 40,000 completed the main series, and 15,000 completed all videos. Of the completers, 70.1% reported reduced anxiety and depression. Mapping PHQ-4 scores to EQ-5D utilities, the average QALY gain was 0.0095 per completer limited to the 20 days of the program. At a willingness to pay threshold of 500K NOK/QALY, the intervention is cost-effective up to NOK 4,700 (400 Euros) per completer. Including improvements up to 6 months, the average QALY gain was 0.068 per completer, with cost-effectiveness up to 34K NOK (2,800 Euros) per completer.

CONCLUSIONS: The TANKEVIRUS app is widely used, with 2.1% of Norway's population engaging in two years. It is associated with reduced anxiety and depression and is cost-effective at 400 to 2,800 Euros per completing user.