Noncompliance with antihypertensive medications: the impact of depressive symptoms and psychosocial factors.

Despite the availability of effective therapy, hypertension remains poorly controlled in the United States and other industrialized countries. In the Third National Health and Nutrition Examination Survey, nearly half of hypertensive patients in the community-based sample were found to be taking no prescription medication, and only one quarter of those who were being treated had their blood pressure adequately controlled.1 Patient noncompliance with prescribed treatments is a central reason for the failure to control hypertension in those receiving therapy.2 Numerous investigations have found that half of hypertensive patients do not comply adequately with treatment, and that half of those with “refractory” hypertension are in fact nonadherent.3–7 Such high levels of noncompliance are of tremendous concern, given the serious consequences of uncontrolled hypertension on cardiovascular, cerebrovascular, and renal morbidity as well as mortality.8 Clearly, interventions to improve adherence with antihypertensive medications are needed. However, if such interventions are to be successfully designed, targeted, and cost-effective, it is critical to understand the complex reasons for nonadherence, and to identify those that are modifiable.9 Investigators have identified some sociodemographic and clinical features associated with compliance (e.g., age, gender, race, education, employment, socioeconomic status, or the presence of specific comorbid conditions such as cardiovascular disease), although the findings are inconsistent. 2,3,10–16 Despite the likelihood that psychosocial and behavioral characteristics may be important determinants of compliance, few rigorous studies have defined the impact of these features on adherence; those that have been conducted have produced inconsistent results. The variable receiving the most attention has been patients' health beliefs, including their perceptions of the threat posed by the condition, the effectiveness of treatments, and the importance of complying with therapy.17–19 Other psychosocial variables thought to influence antihypertensive medication adherence include: knowledge of hypertension and its treatment14,20; social support21,22; satisfaction with health care10,23,24; and the locus of control (i.e., the degree to which a patient feels that control over their circumstances is internal or external).25 Behaviors that have been examined and related to compliance with blood pressure medication have included use of alcohol or substances2,26 and smoking.14 The effect of psychopathology on compliance with medications for other cardiovascular conditions has been considered, but rigorous study of such relationships has been limited.27 Unfortunately, few studies of the relationships between psychosocial factors and compliance with antihypertensives have been adequately powered, simultaneously adjusted for other determinants of compliance, or conducted in typical clinical populations; and few have used precise assessments of compliance. Therefore, in the current study, we employed typical outpatient populations and an objective measure of compliance to test the hypothesis that believing in the importance of treating hypertension, possessing greater knowledge, having more social support, being more satisfied, having a more external locus of control, responding in a more socially desirable manner, having fewer depressive symptoms, and consuming less alcohol or tobacco would all be associated with greater compliance with antihypertensive medications. Although our hypothesis was limited to the independent effects on compliance of these understudied psychosocial and behavioral variables, we also considered it essential to adjust for more established determinants including demographic, clinical, and health care utilization variables.