The development of the Self-Medicating Scale (SMS): a scale to measure people’s beliefs about self-medication

Objective We describe the development of a reliable and valid measure of people’s beliefs about self-medication. To achieve this, student self-medication beliefs and behaviours in response to acute pain were investigated. Specific objectives were to establish the internal reliability plus content and construct validity of this scale. Method The nine item ‘Self-Medicating Scale (SMS)’ was developed following one to one interviews conducted with a purposive sample of 10 lay people in 2001 to explore their self-medicating beliefs and behaviour. The SMS was completed by 304 undergraduate pharmacy students in March 2006, along with measures of self-reported over the counter (OTC) analgesic use, pain severity and other non-pharmacological methods of pain relief, using a cross-sectional design. Exploratory factor analysis was conducted on SMS items using Maximum Likelihood extraction and Varimax rotation. Main outcome measure Factor structure of the SMS and relationships between SMS scales and medication-taking behaviour. Results Factor analysis of the SMS revealed three factor structures which were named ‘Reluctance’, ‘Don’t think twice’ and ‘Run its course’ (each three item scales with good Cronbach’s alpha 0.82, 0.77 and 0.75 respectively). Of the 304 respondents, 93% reported having experienced pain over the past month and nearly three quarters of these indicated that they had self-medicated with OTC analgesics (mean 10.8 doses). Statistically significant differences or associations were found in all three SMS scores and each of the main outcome variables i.e. whether or not analgesics were taken, number of doses of OTC analgesics taken and number of non-pharmacological remedies tried. Conclusions These results show that the SMS possesses good internal reliability, plus good content and construct validity indicating that it is a useful measure of self-medication beliefs. More work is needed to extend these findings to the wider general public and with other OTC medications.