Chronic whiplash is a burden both to the individual and to the health care system in most western countries. The condition is characterized by a great variety of symptoms from all over the body, apparently without attending objective signs, making it difficult to relate the symptoms to the neck injury. The symptoms are persisting, in spite of different treatment approaches and are associated with gross disability and psychosocial problems. It has been difficult to explain these findings and that is where scientific debate has centred. Two opposing models have been proposed: the organic model, which explains the symptoms with the mechanical forces transmitted during a collision, and the functional somatic model, which explains the symptoms as expression of psychosocial factors and a sick role adopted of the individual. The aim of the thesis is to explore hypotheses derived from the functional somatic model: that whiplash is associated with an increased prevalence of anxiety and depression and that pre-injury anxiety and depression predict subsequent report of whiplash, that pre-injury poor health is associated with the report of whiplash, and that chronic whiplash is characterized by a great array of different symptoms. Finally, it is an aim to explore the association between self-reported whiplash and subsequent disability pension award.
All studies in the thesis are based on the Health Study of Nord-Trøndelag (HUNT), which is a large population-based survey. The first two studies used cross-sectional designs based on the HUNT 2 study (1995-97), while the last two studies had a prospective longitudinal design, including baseline data from the HUNT 1 study (1984- 86) and outcome data from the HUNT 2 study. Information on whiplash was included in the HUNT 2 study. In the two prospective studies, the whiplash group was restricted to individuals reporting a whiplash injury between HUNT 1 and HUNT 2. To explore the predictive significance of self-reported whiplash for later disability award, we used baseline data from the HUNT 2 study and outcome data from the Registries of the National Insurance Administration. In all the studies, we used binary logistic regression to explore our research questions, adjusting for possibly confounding factors like age,gender, education, marital status and alcohol problems. Information on anxiety and depression was based on two different instruments: the Anxiety and Depression Index – 12 (ADI-12) in the HUNT 1 study and the Hospital Anxiety and Depression Scale (HADS) in the HUNT 2 study. Information on symptoms, diagnoses, subjective health, use of health services and use of medication were self-reported without objective confirmation.
We found, in the first study, an increased prevalence of anxiety disorder and depression in individuals reporting whiplash injuries happening more than two years ago. The increased prevalence of these disorders was partly explained by neck pain and headache, which was in accordance with findings from other chronic pain disorders. This conclusion was further explored in the second study where we compared the symptom profile of chronic whiplash with the profile of two chronic pain disorders, an organic pain disorder (rheumatoid arthritis) and a functional somatic pain disorder (fibromyalgia). Results indicated that the symptom profile of chronic whiplash was more alike the profile of fibromyalgia than rheumatoid arthritis. The chronic whiplash group had a significantly higher prevalence of symptoms from all body parts, across all organ systems, and also mental symptoms, compared to a control group without fibromyalgia, rheumatoid arthritis and whiplash. The fibromyalgia group had an even higher prevalence of all symptoms than the whiplash group, while the rheumatoid arthritis group showed an increase in particularly pain and stiffness symptoms. The perception of chronic whiplash as a functional somatic disorder was further explored in the third and the fourth study by examining the predictive significance of pre-injury health on the report of whiplash. We found, in the third study, that pre-injury anxiety and depression predicted the report of whiplash. The strength of the association of preinjury case-level anxiety and depression with incident whiplash was comparable to the previously reported cross-sectional association of anxiety and depression with chronic whiplash in the first study. Also pre-injury health, as a broader concept, was also strongly associated with incident whiplash and particularly with “whiplash with neck pain”. The association between pre-injury health and ‘whiplash with neck pain’ could not be explained by the neck pain. Finally, the third study indicated a strong association between self-reported whiplash and subsequent disability pension award, even in the absence of neck pain. Conclusions Whiplash is a complex disorder which is associated with symptoms of poor health and impairment already before the trauma, and which demonstrates a wide array of symptoms from all over the body after the injury. Pre-injury anxiety and depression predicts subsequent self-reported whiplash and individuals with whiplash have an increased prevalence of anxiety and depression long time after the injury. Award of disability pension is increased following self-reported whiplash, even in the absence of neck pain. This picture seems to give strongest support to the functional somatic model of chronic whiplash.