Which type of studies can show a relationship between factors but do not establish a cause-and-effect link?

Observational studies are designed to identify and analyze relationships between variables without manipulating any of the studied factors. In these studies, researchers observe and collect data on subjects in their natural environments, allowing them to identify correlations or associations between factors. However, because these studies do not involve interventions or controlled conditions, they cannot definitively establish cause-and-effect relationships.

For example, an observational study may find that there is a relationship between high levels of stress and increased incidence of health problems, but it cannot conclude that high stress causes these health issues. Other unmeasured variables could influence this relationship, which is a limitation of this study design.

In contrast, controlled and randomized controlled studies involve interventions where researchers can manipulate variables and apply statistical methods to determine causality. Anecdotal studies, while they provide individual accounts, lack systematic analysis and do not support robust conclusions about relationships or causation. Thus, observational studies are key in identifying potential leads for further research but do not establish direct causal relationships.