  We describe a case study with the participation of a Danish veteran suffering
from post-traumatic stress disorder (PTSD). As part of psychotherapeutic
treatment the participant and therapist have used our novel technique for
instrumenting self-tracking of select aspects of subjective experience using a
one-button wearable device. The instrumentation system is described along with
the specific self-track- ing protocol which defined the participant's
self-tracking of a single symptom, namely the occurrences of a bodily
experienced precursor to hyperarousal. Results from the case study demonstrate
how self-tracking data on a single symptom collected by a patient can provide
valuable input to the therapeutic process. Specifically, it facilitated
identification of crucial details otherwise unavailable from the clinical
assessment and even became decisive in disentangling different symptoms and
their causes.
