PRIVACY: That mental health app might share your data without telling you.

By intercepting the data transmissions, they discovered that 92 percent of the 36 apps shared the data with at least one third party — mostly Facebook- and Google-run services that help with marketing, advertising, or data analytics. (Facebook and Google did not immediately respond to requests for comment.) But about half of those apps didn’t disclose that third-party data sharing, for a few different reasons: nine apps didn’t have a privacy policy at all; five apps did but didn’t say the data would be shared this way; and three apps actively said that this kind of data sharing wouldn’t happen. Those last three are the ones that stood out to Steven Chan, a physician at Veterans Affairs Palo Alto Health Care System, who has collaborated with Torous in the past but wasn’t involved in the new study. “They’re basically lying,” he says of the apps.

The researchers don’t know what these third-party sites were doing with this user data. “We live in an age where, with enough breadcrumbs, it’s possible to reidentify people,” Torous says. It’s also possible the breadcrumbs just sit there, he says — but for now, they just don’t know. “What happens to this digital data is kind of a mystery.”

You don’t have to be a user of Facebook’s or Google’s services for them to have enough breadcrumbs to ID you.