Changes in Outpatient Healthcare Utilization and Costs Following Mild Traumatic Brain Injury among Service Members in the Military Health System by Preexisting Behavioral Health Condition Status.

Objective:To evaluate changes in healthcare utilization and cost following an index mild traumatic brain injury (mTBI) diagnosis among service members (SMs). We hypothesized that differences in utilization and cost will be observed by preexisting behavioral health (BH) diagnosis status.Setting:Direct care outpatient healthcare facilities within the Military Health System.Participants:A total of 21 984 active-duty SMs diagnosed with an index mTBI diagnosis between 2017 and 2018.Design:This retrospective study analyzed changes in healthcare utilization and cost in military treatment facilities among SMs with an index mTBI diagnosis. Encounter records 1 year before and after mTBI were assessed; preexisting BH conditions were identified in the year before mTBI.Main Measures:Ordinary least squares regressions evaluated difference in the average change of total outpatient encounters and costs among SMs with and with no preexisting BH conditions (eg, posttraumatic stress disorder, adjustment disorder). Additional regressions explored changes in utilization and cost within clinic types (eg, mental health, physical rehabilitation).Results:There was a 39.5% increase in overall healthcare utilization during the following year, representing a 34.8% increase in total expenditures. Those with preexisting BH conditions exhibited smaller changes in overall utilization (& beta;, -4.9; [95% confidence interval (CI), -6.1 to -3.8]) and cost (& beta;, $-1873; [95% CI, $-2722 to $-1024]), compared with those with no BH condition. The greatest differences were observed in primary care clinics, in which those with prior BH conditions exhibited an average decreased change of 3.2 encounters (95% CI, -3.5 to -3) and reduced cost of $544 (95% CI, $-599 to $-490) compared with those with no prior BH conditions.Conclusion:Despite being higher utilizers of healthcare services both pre- and post-mTBI diagnosis, those with preexisting BH conditions exhibited smaller changes in overall cost and utilization. This highlights the importance of considering prior utilization and cost when evaluating the impact of mTBI and other injury events on the Military Health System.