Sequential analysis of autonomic arousal and self-injurious behavior.

Swettenham et al. (2013) watched three adults with intellectual disability second-by-second. Each wore a tiny heart-rate monitor. The team logged every self-injury hit, bite, or head bang at the same time. They wanted to see if heart rate changed right before or after each act.

This was a single-case design. No treatment was given. The goal was pure discovery: map the moment-to-moment dance between body arousal and SIB.

Every participant showed a clear pattern. Heart rate jumped or dropped within seconds of each SIB episode. The link was immediate and reliable. High-frequency heart-rate variability (HF-HRV) also shifted, showing quick parasympathetic swings.

In plain words: the body warned you a blow was coming, and it reacted again right after. Track the heart and you track the behavior.

Northrup et al. (2022) later repeated the same second-by-second method with autistic youth in a hospital. They found SIB often showed up before visible emotion dysregulation, not after. Together the two studies paint a timeline: internal arousal shifts first, SIB follows, overt distress comes last.

Foti et al. (2015) and Ferguson et al. (2025) both call for adding biological data to SIB assessments. Swettenham et al. (2013) gives the live demo those reviews asked for—heart metrics right beside behavior.

Guy et al. (2014) looked at resting heart rhythms in autistic kids and saw lower RSA linked to anxiety. John’s moment-to-moment data adds: when RSA plunges second-by-second, SIB may erupt seconds later.

You can borrow a sports heart-rate strap and pair it with your ABC data. Watch for sudden jumps or drops that repeat before SIB. Those seconds are your new cue to deliver a replacement response, sensory break, or calming prompt. You turn an invisible bodily event into a visible, treatable signal.