  Passively collected behavioral health data from ubiquitous sensors holds
significant promise to provide mental health professionals insights from
patient's daily lives; however, developing analysis tools to use this data in
clinical practice requires addressing challenges of generalization across
devices and weak or ambiguous correlations between the measured signals and an
individual's mental health. To address these challenges, we take a novel
approach that leverages large language models (LLMs) to synthesize clinically
useful insights from multi-sensor data. We develop chain of thought prompting
methods that use LLMs to generate reasoning about how trends in data such as
step count and sleep relate to conditions like depression and anxiety. We first
demonstrate binary depression classification with LLMs achieving accuracies of
61.1% which exceed the state of the art. While it is not robust for clinical
use, this leads us to our key finding: even more impactful and valued than
classification is a new human-AI collaboration approach in which clinician
experts interactively query these tools and combine their domain expertise and
context about the patient with AI generated reasoning to support clinical
decision-making. We find models like GPT-4 correctly reference numerical data
75% of the time, and clinician participants express strong interest in using
this approach to interpret self-tracking data.
