Objectives: To estimate adherence to lithium in a nationwide sample of all patients treated with lithium and to characterize adherence according to gender and age.
Methods: Adherence to lithium was estimated using data obtained by linking Medicinal Product Statistics with the Danish Medical Register on Vital Statistics, identifying all persons who received lithium among the 5.3 million persons living in Denmark during the period 1995 to 2000 inclusive.
Results: The median time to discontinuation of lithium was 181.0 days [95% confidence interval (CI) 135.7–181.0] and 25% of patients stopped treatment with lithium within 45.2 days. Adherence to lithium was significantly poorer for women (135.7 days; 95% CI 90.5–135.7) than for men (316.7 days; 95% CI 271.4–407.1) and for younger (18–39 years) and older (≥60 years) patients compared to middle-aged patients.
Conclusions: The results highlight the need for increased focus on long-term adherence to lithium with intensified psychological support, especially among younger and older female patients.