What causes disease?
For any "disease" or condition, you could start by considering interactions among environmental and social factors:
Poor diet, resulting from food choices, "causes" nutritional deficiency or obesity in a population
. . . Keep swimming upstream!
Also, consider that how issues are framed is influenced by our assumptions and biases.
It may be useful to have a structure to help guide you when searching.
When you formulate a research question, consider these elements:
Note: It is possible that not all of the above elements will be appropriate for your search topic.
This exercise (PDF) will take you through the process of formulating a search
PICO is another popular way to structure a search.
PICO stands for Patient or Population; Intervention; Comparison or Control; Outcome.
Embase has a PICO Search option.
Considering the question a research article addresses may help you determine if it's relevant to your needs.
Below are some examples of questions or lines of inquiry:
Compare these two questions, to help evaluate any intervention studies you read:
Finding a systematic review that addresses the question you are interested in can be very helpful
Primary research presents original research methods or findings for the first time. A primary source is a document (or object) which was written or created during the time under study, by someone who was present during an experiment or experience, and offers an firsthand view of a particular event. Especially in the sciences, an "experience" or "event" includes a research study or process.
In science, primary literature is the original publication of a scientist's new data, results, and theories.
A good way to evaluate whether or not a scientific article is a primary source is whether the article has a Materials and Methods (or similar) section. If the article discusses methods, it is likely primary literature.
Secondary literature does not report new findings, and includes review articles and most scholarly or academic books, including textbooks.