Although diabetes mellitus (DM) is treatable, it is still not curable. Its chronicity is associated with a high prevalence of psychiatric disorders, especially depression in type 2 DM and learned helplessness in type 1 DM. In turn, this depression and helplessness may affect a patient's adherence to medical appointments, compliance to treatment, and effective doctor-patient relationships, which are vital to promising outcomes. This study reviews the existing literature regarding the interactional relationships between depression, DM and the doctor/patient relationship, and also suggests certain aspects of the doctor/patient relationship which can contribute to more successful treatment outcomes.