Final answer:
The most commonly reported reason for poor adherence to medical advice is lack of positive feedback.
Step-by-step explanation:
According to Dunbar-Jacob et al. (2012), the most commonly reported reason for poor adherence to medical advice is lack of positive feedback. This means that when patients do not receive encouragement or recognition for following their medical advice, they are less likely to continue with the recommended treatment. This can be due to a variety of factors, such as healthcare providers not acknowledging the patient's efforts or the patient not perceiving any improvements in their health.