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The reason why some individuals develop chronic symptoms, whiplash-associated disorder, following whiplash trauma is poorly understood. We explored whether precollision pain-related diagnoses, medically unexplained symptoms, and psychiatric diagnoses are related to whiplash-associated disorder.A cohort of 719 individuals exposed to whiplash trauma and subsequently experiencing symptoms within 72 hours (whiplash-exposed cohort) and 3595 matched controls were included in this observational prospective study. At 12 months postcollision, the whiplash-exposed cohort rated their neck pain using the Visual Analog Scale. Data on health were obtained from the Danish National Patient Register for the whiplash-exposed cohort and for the controls for a 5-year period before collision.The whiplash-exposed cohort had significantly increased incidences of precollision pain-related diagnoses: χ2(1)=17.42, P<0.001 and medically unexplained symptoms: χ2(1)=22.22, P<0.001 but not psychiatric diagnoses: χ2(1)=3.60, P>0.05 compared with controls in the 5-year period. Participants from the whiplash-exposed cohort with precollision pain-related diagnoses (odds ratio=2.46; 95% confidence interval, 1.39; 4.35) and medically unexplained symptoms (odds ratio, 1.72; 95% confidence interval, 1.04; 2.84) had significantly increased odds for neck pain at follow-up.Precollision pain and medically unexplained symptoms predict chronic neck pain following whiplash trauma. This may indicate that a sensitization process was initiated before the collision or that individuals with precollision low threshold for contacting health care services maintain this behavior postcollision. The collision may trigger existing individual vulnerabilities that constitute to be a risk factor for chronic whiplash.