Aim: The purpose of the present study was to identify the psychosocial/pharmacological predictors of antidepressant (AD) adherence.

Methods: An Internet-based survey was conducted among 1151 Japanese individuals with major depressive disorder. Subjects were asked to report their degree of non-adherence for each AD taken using a 5-point Likert scale: 0, never forget; 1, rarely forget; 2, occasionally forget; 3, sometimes forget; and 4, often forget. The highest number reported among each subject was assigned as their low adherence index (LAI). Individuals with an LAI > or = 3 were defined as members of the low adherence (LA) group. Predictors of LA was analyzed using bivariate and multivariate models, both among the total number of subjects and single AD subgroup (n = 657).

Results: Nearly one-third of subjects (n = 381, 33.1%) reported LA. On bivariate analysis, LA was associated with lower age, worker or student status (vs unemployed or housewife), higher daily dosing frequency (DDF), low drug satisfaction, and a neutral/negative doctor-patient relationship (DPR; P < 0.001). In a multivariate model, LA was predicted by age (< or =34 years: odds ratio [OR], 1.64), worker or student status (OR, 1.87), higher DDF (> or =twice daily: OR, 1.61), and neutral/negative DPR (OR, 1.54; P < 0.01). Among the single-AD subgroup, adherence was similar between those on selective serotonin reuptake inhibitors/serotonin-noradrenaline reuptake inhibitors and tricyclics. Use of neither medication was associated with adherence in a multivariate model.

Conclusion: LA was predicted by lower age, worker or student status, higher DDF, and neutral/negative DPR. Adherence was not significantly different between subjects on newer agents and tricyclics.