The role of tonic immobility in trauma treatment

BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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. RESULTS: 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. DISCUSSION: 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.