The Severity of Dependence Scale detects people with medication overuse: the Akershus study of chronic headache

Objective: To evaluate the Severity of Dependence Scale (SDS) in people with primary chronic headache and analyse the pattern of medication overuse. Design: Cross sectional epidemiological survey. A posted questionnaire screened for chronic headache. Neurological residents interviewed those with self-reported chronic headache. The International Classification of Headache Disorders was used. Split file methodology was employed for data analysis. Setting: Akershus University Hospital, Oslo, Norway. Participants: A random sample of 30 000 people, aged 30-44 years, from the general population of Akershus County, Norway. 405 people had primary chronic headache. Main outcome measure: SDS score in those with and without medication overuse. Results: The screening questionnaire response rate was 71% and the participation rate of the interview 74%. Among 405 people with primary chronic headache, 95% had chronic tension-type headache, 4% had chronic migraine and <1% had other primary chronic headaches. Of 386 persons with chronic tension-type headache, 44% had medication overuse and 47% had co-occurrence of migraine. Simple analgesics, combination analgesics, triptans, ergotamine, opioids and a combination of acute medications were overused by 65%, 27%, 4%, <1%, 1% and 2% of people, respectively. The mean SDS score was significantly higher in those with than in those without medication overuse (5.6 vs 2.7; p < 0.001). Conclusion: The SDS questionnaire detects medication overuse and dependency-like behaviour in persons with primary chronic headache.