In the world of digital health, Silicon Valley-based Mindstrong stands out. It has a remarkable team and tens of millions of funding. It also has a fascinating idea-its app, based on mental functioning research, can help detect troubling mental health patterns by collecting data on person’s smartphone usage-how quickly they type, for instance.

The company’s app collects information about how people are typing and runs it through a machine learning algorithm (计算程序) to determine which data can predict their emotional state. The idea is to use that data to establish a “normal” pattern-so it can be compared with someone’s typing habits on any given day. If the habits change, slower or more anxious than normal, the app can warn a health care provider.

The promise of this technology has made Mindstrong incredibly popular since it was launched last year; already more than a dozen counties in California have agreed to apply the company’s app to patients. Does the app live up to its promise? There’s no way to tell. Almost no one outside the company has any idea whether it works, leading some experts to wonder if the technology is ready for the real world. “I wouldn’t waste all that time and money in the wild until they get sure that some of those things are as specific as they hope they are,” said Rosalind Picard, a researcher at MIT Media Lab, who is familiar with Mindstrongs work.

“It has passed the gold-standard clinical tests for depression and anxiety,” said Dr. Paul Dagum, the company’s founder. “We’re confident, and we’re already seeing some really exciting results.” Mindstrong officials said that among their most encouraging results is that its app can even predict how a person will feel next week, kind of like a weather app for your mood. “For a clinician(临床医生) or someone looking after a patient, they know that it could be very, very powerful,” Dagum said.

After his father was rushed to the hospital, Yanatha Desouvre began to panic. So he did the one thing he knew would calm himself: He wrote. Over the next few weeks, Desouvre filled several notebooks, writing about his worry as well as his happy memories with his dad. “Writing allowed me to face my fear,” says Desouvre, “My pen was a tool to process the pain.”

He is in good company. An extensive body of research shows benefits to writing about a traumatic (创伤) experience in a manner that psychologists refer to as “expressive writing.”James Pennebaker, a psychology professor, says that studies have looked at the potential benefits of expressive writing and found that it can strengthen the immune system, including for people with illnesses such as cancer, depression, and PTSD(创伤后应激障碍). It can also help reduce chronic pain(慢性痛), and improve mood, sleep, and memory. And it may even help reduce symptoms of depression and PTSD.

Expressive writing works because it allows you to make meaning out of a painful experience, experts say. It can be a powerful coping tool for many, in large part because it helps reduce the secrecy people often feel about a trauma, as well as their reluctance to face emotions. The mere act of labeling a feeling—of putting words to an emotion—can hold back the neural activity in the threat area of the brain. Writing can increase someone’s acceptance of their experience, and acceptance is calming.

Recognizing that something is bothering you is an important first step. Translating that experience into language forces you to organize your thoughts. And creating a narrative gives you a sense of control.