Unexpected symptoms after concussion: Potential links to functional neurological and somatic symptom disorders.

OBJECTIVE Reporting of unexpected symptoms after concussion might, in some people, reflect a Functional Neurological Disorder (FND), Somatic Symptom Disorder (SSD), or exaggeration (feigning). This study aimed to determine whether reporting unexpected symptoms after concussion was associated with risk factors for FND/SSD, exaggeration, or both. METHOD Adults with persistent symptoms following concussion (N = 77; 61% women) rated the presence and severity of unexpected neurological symptoms (from the Screening for Somatoform Symptoms scale, e.g., paralysis) and somatic symptoms (from the Patient Health Questionnaire-15, e.g., stomach pain) that did not overlap with post-concussion symptom scale items. The independent variables were risk factors for exaggeration (neuropsychological performance validity test failure and personal injury litigation) and predisposing and perpetuating factors for developing FND and/or SSD (e.g., fear avoidance behavior). RESULTS When adjusting for all covariates, fear avoidance behavior was most strongly related to unexpected neurological symptoms (B = 0.11, 95% confidence interval = 0.05-0.18, p < .001), while current anxiety scores were most strongly related to unexpected somatic symptoms (B = 0.34, 95% confidence interval = 0.15-0.52, p < .001). Performance validity test failure and litigation were not significant predictors in either model. CONCLUSION Unexpected neurological and other somatic symptoms after concussion should not be dismissed as exaggeration. Psychological factors thought to perpetuate FND and SSD (e.g., fear avoidance behavior) may contribute to unexpected symptoms following concussion. More research is needed at the intersection of FND, SSD, and persistent post-concussive symptoms.