ObjectivesTo assess the trends in medication use indicative of physical and psychological morbidity following the 2010 volcanic eruption in Eyjafjallajökull immediately after and during a 3-year period following the eruption.DesignPopulation-based register study.SettingEyjafjallajökull eruption in Iceland, 2007–2013.ParticipantsAll residents in Iceland who received at least one medication dispensing were identified. Residents of exposed areas were classified into exposure groups (individual-level data) and residents in other parts of Iceland were included as a non-exposed group (aggregated data).Intervention/exposureEyjafjallajökull erupted on 14 April 2010 and continued for 39 days, producing heavy ash fall in South Iceland.Main outcome measuresUsing interrupted time series analysis, we examined annual and quarterly changes in medicine use, measured as number of dispensed defined daily dose (DDD) per 1000 individuals. We calculated the level shift (immediate change) and change in slope from pre-eruption to post-eruption (long-term change) in medication dispensing.ResultsAmong exposed residents, there was a 6% decrease (95% CI -7% to -4%) in the annual number of dispensed DDDs 1-year post-eruption in the overall medication class, including analgesics (−5%, 95% CI -6% to -3%), hypnotics and sedatives (−9%, 95% CI -11% to -7%) and respiratory medications (−7%, 95% CI -9% to -5%; −8%, 95% CI -11% to -4%). Simultaneously, there was a 9% decrease (95% CI -14% to -4%) in the overall medication class among non-exposed residents. Moreover, among exposed residents, we observed change in slope of −4% (95% CI -7% to -1%) in the overall medication class, including for analgesics (−6%, 95% CI -8% to -3%) and other respiratory drugs (−10%, 95% CI -16% to -4%).ConclusionOur findings indicate that the eruption did not lead to increases in medication dispensing among residents of exposed areas, rather decreases for some medicine classes. The results should be interpreted with caution since the content of each eruption differs.