The Utility of the Mayo-Portland Adaptability Inventory Participation Index (M2PI) in US Military Veterans With a History of Mild Traumatic Brain Injury.

Objective: To examine the utility of the Mayo-Portland Adaptability Inventory-4th Edition Participation Index (M2PI) as a self-report measure of functional outcome following mild traumatic brain injury (mTBI) in US Military veterans.

Setting: Department of Veterans Affairs Polytrauma Rehabilitation Center specialty hospital.

Participants: On hundred thirty-nine veterans with a history of self-reported mTBI.

Design: Retrospective cross-sectional examination of data collected from regular clinical visits.

Main Measures: M2PI, Neurobehavioral Symptoms Inventory with embedded validity measures, Posttraumatic Stress Disorder Checklist-Military Version.

Results: Forty-one percent of the sample provided symptom reports that exceeded established cut scores on embedded symptom validity tests. Invalid responders had higher levels of unemployment and endorsed significantly greater functional impairment, posttraumatic stress symptoms, and postconcussive complaints. For valid responders, regression analyses revealed that self-reported functioning was primarily related to posttraumatic stress complaints, followed by postconcussive cognitive complaints. For invalid responders, posttraumatic stress complaints also predicted self-reported functioning.

Conclusion: Caution is recommended when utilizing the M2PI to measure functional outcome following mTBI in military veterans, particularly in the absence of symptom validity tests.