The role of tonic immobility in trauma treatment

Tonic Immobility (TI) is an involuntary response to extreme stress, linked to the onset and severity of PTSD and potentially interfering with recovery. TI may also occur during re-experiencing of trauma, where it has been shown to mediate the impact of peritraumatic TI on PTSD severity in untreated patients. However, the influence of TI - whether peritraumatic or during re-experiencing - on trauma-focused treatment outcomes remains unclear.

This study examined whether peritraumatic TI predicts changes in PTSD symptoms during trauma-focused treatment. We hypothesized that higher peritraumatic TI would be associated with smaller reductions in PTSD symptoms and that this relationship would be mediated by TI during re-experiencing. Additionally, we expected decreases in TI during re-experiencing to correlate with symptom improvement.

Seventy-four patients in an intensive PTSD program completed self-report measures on peritraumatic TI and TI during re-experiencing. PTSD severity was assessed with the CAPS-5 and PCL-5. Analyses examined associations between peritraumatic TI and PTSD symptom change, with mediation tested through pretreatment and pre-post TI scores during re-experiencing.

Peritraumatic TI was not significantly related to changes in PTSD symptoms, and no mediation effects were observed. However, decreases in TI during re-experiencing were positively correlated with PTSD symptom reduction. Peritraumatic TI did not show a statistically significant association with baseline PTSD severity.

Findings suggest that patients with strong TI responses benefit equally from trauma-focused treatment, and reductions in TI during re-experiencing may be associated with greater symptom improvement.