Hypertension is highly prevalent and often requires medication to control blood pressure in order to prevent subsequent cardiovascular diseases (Kearney et al., 2005). Adherence to antihypertensive drugs, i. e., the degree to which a patient correctly follows the treatment plan, is poor and should be improved (Naderi et al., 2012). Therefore, fostering desired (unspecific) drug effects (placebo effects), while preventing nocebo effects (e.g. the aggravation of side effects) is focused (Rief et al., 2011). Negative treatment expectations can be operationalized as beliefs about medicines, which are also directly associated with drug adherence (Foot et al., 2016). To foster unspecific effects, a robust placebo effect on blood pressure needs to be proven. Therefore, we carried out a meta-analysis of all accessible randomized controlled trials on beta-blocker therapy in patients with hypertension. Studies were supposed to have a parallel-group design including a placebo condition. In a total of 23 studies (11.067 patients), the placebo effect was robust and accounted for 34% (systolic) and 47% (diastolic) of the blood pressure lowering drug effect. In the second study, nocebo effects were addressed via truthful verbal information. Therefore, 80 healthy participants were randomized into one of two framing groups: in the positive framing group, participants were told that dizziness was an onset sensation of a beta-blocker, while the control group received a standard information about dizziness as a common side effect. After administration of 100 mg metoprolol, participants in the positive framing group rated drug-specific side effects significantly less threatening. Subgroup analysis revealed that participants who believed that medication is harmful benefited from positive framing compared to neutral framing regarding the total number of occurrences, the intensity, and perceived threat of specific drug-attributed side effects. In the third study, the online surveys of 273 patients with hypertension were analyzed regarding several beliefs about the specific medication in explaining variance in drug adherence. The structural equation model was of acceptable fit and confirmed the important role of specific beliefs about medicines. The model explained 23% of variance in adherence via the necessity-concern framework and several background variables such as emotionally supportive doctor-patient communication. The results of this thesis emphasize that fostering unspecific treatment effects while addressing negative expectations personalized are essential for the improvement of blood pressure control in hypertension. To do so, there seems to be a lot of potential in improving doctor-patient communication.