A handful of these apps (which revolved around issues like depression and quitting smoking) shared particularly sensitive data like health diaries and voluntary substance use reports. As the University of Toronto's Qunn Grundy (not involved in the study) told The Verge, this info could give outsiders a picture of your mental health that you might not want to share. You might see ads for health consultations or even addictive substances.

The immediate solution is a familiar one: verify that an app has a privacy policy, and check to see where your data is going before you use the app in earnest. Study co-author John Torous also suggested sticking to apps from more trustworthy sources like health care providers and the government. In the long term, though, there may need to be stricter requirements to ensure that your health information only goes where it's truly necessary.