The Bonn team of psychologists and computer scientists, led by Alexander Markowetz, studied the smartphone habits of 50 students for six weeks. More than a quarter of the students used their phones at least two hours a day, and checked them, on average, every 12 minutes.
 

Drawing on the findings, the team developed a free app called Menthal that monitors your smartphone usage and tells you how long you spend on the phone per day, as well as which apps you use the most.

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But CNET reports the app has another use: Measuring the progress and severity of mental illnesses such as depression, based on a personality analysis tied to such factors as how much time you spend messaging, hanging out on Facebook and chatting with friends.

Those who spend a lot of time engaging in such activities may be more cheerful and gregarious, while fewer interactions could mean that you are feeling depressed and closed off from the world.
 

The free app can be downloaded from the Google Play store or the Methal Website.