Why are case reports considered weak evidence?

Case reports are regarded as weak evidence primarily due to their lack of control and generalizability. A case report typically details the clinical experience of an individual patient or a small group, focusing on unique presentations of disease or responses to treatment. The absence of control groups limits the ability to draw robust conclusions or establish cause-and-effect relationships, which is crucial in evidence-based medicine.

Moreover, because case reports often involve specific patients, their findings cannot be easily generalized to a broader population. This restriction impacts the external validity of the information shared. Unlike larger trials that study diverse demographics and employ randomization to control for confounding variables, case reports do not offer the same level of reliability or applicability to wider populations. As a result, they stand as less authoritative evidence compared to more rigorous forms of research such as randomized controlled trials or systematic reviews.