A test of theory of planned behavior in type II diabetes adherence: The leading role of perceived behavioral control İlknur Dilekler 1 & Canay Doğulu 2 & Özlem Bozo 3 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Diabetes mellitus is a health complication that millions of people suffer from all over the world. Type II (non-insulin dependent) diabetes requires many changes in the daily lives of patients, including monitoring blood glucose, following a healthy diet, exercising, and taking medications. Although it is vital for their health, patients generally find it difficult to adhere to their medical regimen. In order to better understand the adherence behaviors of type II diabetes patients, the theory of planned behavior (TPB) was used as the theoretical framework for this study. Ninety type II diabetes patients, who were outpatients of four different hospitals in Ankara, Turkey were administered the TPB tool. The mediation analyses provided support for the mediating role of intention for the attitudes-behavior and subjective norms-behavior relations. The findings did not reveal a mediating role of intention for the PBC-behavior relation but a significant direct effect of PBC on adherence behavior was found. Overall, it seems important that PBC and the multi-faceted nature of adherence behaviors are considered when designing interventions for type II diabetes patients. Keywords Type II diabetes . Adherence . The theory of planned behavior . Perceived behavioral control . Turkey Chronic diseases have become an important agenda for health practitioners as they, throughout the world, com- prise the major causes of death and disability and there has been an increasing trend in rates of chronic diseases (World Health Organization; WHO 2018). According to worldwide statistics of WHO (2016), the estimated num- ber of people living with diabetes went up from 108 mil- lion to 422 million, reflecting a nearly doubled increase in global prevalence. As these statistics indicate, diabetes is a highly prevalent and rapidly increasing chronic disease. In Turkey, diabetes is among the top ten causes of death and has the highest burden of disease along with cardio- vascular diseases (WHO 2015). Overall, diabetes is glob- ally considered as a serious public health problem that needs to be prevented by controlling related common bi- ological and behavioral risk factors (WHO 2018). Diabetes is a serious chronic condition resulting from body’ s inability to maintain glucose homeostasis. Type II di- abetes, comprising a great majority of people with diabetes, occurs when the body is not able to effectively use the insulin it produces (WHO 2016). If not controlled, diabetes causes raised blood glucose and this leads to many physical compli- cations in the body, such as heart attack, stroke, kidney failure, leg amputation, vision loss, and nerve damage (American Diabetes Association 2000; WHO 2016). The physical com- plications may also be accompanied by psychosocial compli- cations such as negative mood (Adriaanse et al. 2005), depres- sion (Lustman and Clouse 2005), isolation (Whiting et al. 2006), and lower perceived quality of life (Caldwell et al. 1998). Thus, in order to prevent these complications that chal- lenge patients’ daily lives, at the individual level, diabetes need to be managed by following medical adherence and adopting healthy lifestyles targeted at improving diet and physical activity (WHO 2016). Diabetes adherence, which is basically the degree of agreement between the health-related behavior of an individual with the recommended action or advice proposed by health care providers, includes glucose monitoring, administration of medication, healthy diet, foot care, and physical activity (Albery and Munafò 2008). However, due to its complex treatment taking place over a * Canay Doğulu canaydogulu@gmail.com 1 Psychological Counseling and Development Center, Bilkent University, 06800 Bilkent, Ankara, Turkey 2 Department of Psychology, Başkent University, Bağlıca Yerleşkesi, Eskişehir Yolu 18. km., 06790 Etimesgut, Ankara, Turkey 3 Department of Psychology, Middle East Technical University, Üniversiteler Mahallesi, Dumlupınar Bulvarı No: 1, 06800 Ankara, Turkey Current Psychology https://doi.org/10.1007/s12144-019-00309-7