Is your topic researchable?
What causes disease?
For any "disease" or condition, you could start by considering interactions among environmental and social factors.
Let's talk about indexing!
Indexing facilitates more precise search statements, especially for topics that are vague or ambiguous.
The Literature Review Matrix (below) may help you organize what you find in your literature search. This matrix is a simplified version from Health Sciences Literature Review Made Easy (see book below). Older editions of this book are available at the Public Health Library, Optometry Library, and the Social Research Library.