Objective: To apply human error theory to explain non-adherence and examine how well it fits.
Method: Patients who were taking chronic medication were telephoned and asked whether they had been adhering to their medicine, and if not the reasons were explored and analysed according to a human error theory.
Results: Of 105 patients, 87 were contacted by telephone and they took part in the study. Forty-two recalled being non-adherent, 17 of them in the last 7 days; 11 of the 42 were intentionally non-adherent. The errors could be described by human error theory, and it explained unintentional non-adherence well, however, the application of 'rules' was difficult when considering mistakes. The consideration of error producing conditions and latent failures also revealed useful contributing factors.
Conclusion: Human error theory offers a new and valuable way of understanding non-adherence, and could inform interventions. However, the theory needs further development to explain intentional non-adherence.