Epidemiology and psychological factors of whiplash associated disorders in Japanese population.

[Purpose] This study was designed to examine the epidemiological background of Whiplash-associated disorders in Japanese adults and to investigate the psychological factors associated with prolonged treatment for Whiplash-associated disorders. [Subjects and Methods] An online survey was completed by 127,956 participants, of whom 4,164 had been involved in a traffic collision. A random sample of the collision participants (n=1,698) were provided with a secondary questionnaire. From the 974 (57.4%) participants who returned the questionnaire, 183 cases (intractable neck pain treated over a period of 6 months) and 333 controls (minor neck pain treated within 3 months) were selected. Among the control group, the psychological factors associated with prolonged treatment for Whiplash-associated disorders were investigated. [Results] Among the 4,164 collision participants, 1,571 (37.7%) had experienced Whiplash-associated disorders. The prevalence in the general population was 1.2% (1.3% in male and 1.0% in female). Significant differences were observed between the cases and controls for all psychological factors, although both groups had similar distributions of age and gender. [Conclusion] Poor psychological factors were associated with prolonged treatment for whiplash-associated disorders in Japanese adults. These psychological factors should be considered during the treatment of whiplash-associated disorders.