Background Post-concussion, the body is “stressed” as it attempts to restore metabolic and psychologic equilibrium. Elevated stress can be evaluated by disrupted cortisol cycling, perturbations in Heart Rate Variability (HRV), and reported mood disturbance and perceived stress. Assessing stress in concussed athletes may be informative for optimal recovery, safe return-to-play (RTP), and subsequent injury prevention.

Objective To assess the utility of non-invasive stress measures in monitoring concussion recovery.

Design A prospective matched control group design included collection of salivary cortisol, HRV, and two self-report measures: the Profile of Mood States (POMS), and the Perceived Stress Scale (PSS). All measures were taken at three phases of recovery (1. Symptomatic; 2. Asymptomatic; and 3. One-week following RTP). The same protocol was completed by non-injured athletes.

Setting Interuniversity sports teams at a single institution.

Participants 11 athletes, across seven sports, diagnosed with concussion and 11 matched-athlete controls volunteered for the study.

Main outcome measurements Primary outcome measures to test the a-priori hypotheses included: HRV, AM and PM salivary cortisol, Total Mood Disturbance, Depression, Confusion, Fatigue, Vigor, Tension, Anger, and Perceived Stress.

Results A series of 2 (Group) × 3 (Phase) repeated measures ANOVAs revealed significant interactions for HRV and emotional disturbance. Although no emotional disturbance or perceived stress was reported in the asymptomatic phase, concussed athletes displayed altered HRV [increased Low Frequency norm (P=.041) and decreased High Frequency norm (P=.041)]. In addition, significant differences between groups were found for AM cortisol levels one week after RTP (P=.019).

Conclusions Concussed athletes displayed perturbations in HRV, indicating neuroautonomic dysfunction, despite resolution of symptom and mood disturbance. In addition, low levels of morning cortisol following RTP may be indicative of a lingering physiological stress response. These non-invasive markers may be clinically useful in post-concussive recovery assessment and prevention of subsequent injury.