The project will enroll up to 10,000 adult volunteers in individualized experiments (N-of-1 trials) designed to assess the individual-level effects of any of five interventions on three outcomes. The five interventions are: gratitude journaling, mindfulness meditation, random acts of kindness, physical activity, and laughter therapy. The three outcomes are stress, cognitive focus, and happiness. Each participant will engage in the selected activity in 3 day intervals, separated at random by 3 day intervals of usual activity, for a total of six 3-day periods (18 days).

N-of-1 trials (single patient crossover experiments) are a uniquely powerful technique for estimating treatment effects in the individual. N-of-1 trials have been offered to hundreds or perhaps thousands of patients worldwide, but never at scale. HackYourHealth is a tool that supports the conduct of simple N-of-1 self-experiments to test if healthy activities that work in general (i.e., mindfulness meditation, physical activity, gratitude journaling, random acts of kindness, and laughter therapy), improve psychological well-being (stress, focus, happiness) in specific individuals. The tool supplies the experimental design, facilitates data analysis, and channels feedback to participants. The tool is flexible enough to support Massive Individualized N-of-1 Experiments (MINEs) at scale. Working with WNYC Radio in New York City, we will recruit and run 18-day N-of-1 trials up to 10,000 individuals. The purpose of this study is to conduct a formative evaluation of HackYourHealth in terms of its perceived usefulness and to explore heterogeneity in intervention response across the sample. We anticipate that the results will: 1) identify useful behavioral interventions for individual participants; 2) help to estimate generalizable treatment effects for the interventions of interest; 3) assess heterogeneity of treatment effects across subgroups; and 4) elucidate the user experience with N-of-1 trials. When complete, the study will support additional proposals designed to assess the utility of MINEs as applied to additional conditions and treatments.

Inclusion Criteria:

• Age 18 or over
• Living anywhere in the United States
• Using a smartphone
• Having regular access to internet on their phone
• Able to read and write in English

Exclusion Criteria:

There are no exclusion criteria, except that patients with pre-existing cardiovascular disease will be cautioned not to engage in new types of physical activity without consulting a physician.

The analysis will proceed automatically without knowledge of which 3-day treatment periods were associated with one of the five interventions and which were associated with the subject's usual activities.