One novel data stream offered by smartphone digital phenotyping is cognition. While we know that impaired cognition is a core symptom of schizophrenia, and that cognition is affected by depression and anxiety, cognitive symptoms are clinically challenging to quantify. Thus, the cognitive burden of mental illness and the cognitive effects of treatment are often overlooked. However, smartphones are beginning to offer a novel means of capturing a patient’s cognitive state through the use of common clinical tests. For example, the Trail Making Test measures visual attention and executive function by having participants connect dots that differ in number, color, or shape in an ascending pattern.6 By having patients perform this test on a smartphone, clinicians can utilize the touchscreen to capture the user’s discrete actions, such as time to completion and misclicks. These data can be used to build novel measures of cognitive performance that can account for learning bias and other confounding variables.7 While these digital cognitive biomarkers are still in active research, it is likely that they will quickly be developed for broad clinical use.
In addition to the novel data offered by digital phenotyping, another benefit is the low cost and ease of use. Unlike wearable devices such as smartwatches, which can also offer data on steps and sleep, smartphone-based digital phenotyping does not require patients to purchase or use additional devices. Running on patients’ smartphones, digital phenotyping offers the ability to capture rich and continuous health data without added effort or cost. Given that the average person interacts with their phone more than 2,600 times per day,8 smartphones are well suited for capturing large amounts of information that may provide insights into patients’ mental health.
For illnesses such as depression and anxiety, the clinical relevance of digital phenotyping is in the ability to capture symptoms as they occur in context. Figure 2 provides a simplified example of how we can learn that for this fictitious patient, exercise greatly improves anxiety, whereas being in a certain environment worsens it. Other insights about sleep and social settings could also provide further information about the context of the patient’s symptoms. While these correlations alone will not lead to better clinical outcomes, it is easy to imagine how such data could help a patient and clinician start a conversation about making impactful changes.
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