Collabree: An Intervention to Improve the Regularity of Medication Intake

Inclusion Criteria: 1. Informed consent as documented by signature 2. Over 18 years of age at date of randomization 3. Primary or secondary arterial hypertension 4. Patient in an outpatient clinical setting 5. Prescribed a therapy consisting of 4 or more tablets taken per day 6. Stable medication regime that patient has been taking for at least 4 weeks 7. Participant administers their own medications 8. Participant owns a smartphone with a data plan or constant internet access during the study visits and at home to use the application 9. Minimal required smartphone operating system is iOS 12 and Android 8 (Oreo) 10. Adequate communication in German or Swiss-German (all study documentation will only be set to the German language). Exclusion Criteria: 1. Cognitive impairment that limits ability to understand and complete questionnaires 2. Ongoing evaluation for secondary forms of hypertension 3. 3\. Changes in the participant's medication treatment plan after the baseline visit during the intervention period, unless due to a diagnosis of symptomatic hypotension (in-clinic blood pressure below 110/60 mmHg and symptoms of orthostasis or dizziness) or stage 2 hypertension (in-clinic blood pressure \> 160/100 mmHg); after the endpoint (day 90) visit, a change in the treatment plan will be permitted 4. Uncontrolled hypertension (in-clinic blood pressure \> 180/110 mmHg) 5. Inability to operate a mobile phone and the Collabree application 6. Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. 7. Pregnancy or intention to become pregnant in next 6 months 8. Enrollment of the Sponsor or Investigator, their family members, employees and other dependent persons 9. Participation in another clinical trial 10. Physician-estimated life expectancy of less than 6 months