Remember that searching in the databases is different than searching on Google. In Google you can search using a regular English sentence. "What is the connection between organic food and positive mental health?" But in library databases, you need to break down this sentence into individual concepts, and create search terms from the concepts. For example, we could search on the question about organic food and mental health with the search terms "Organic Food", "Mental Health" and "Study". The search terms "Study" means that we want to see any research on those connections.
It will also help your research to think about different ways that different authors might write about the same concept. Sometimes an author will use a synonym or similar word to discuss the same concept. A good way to help think through these search term options is to create a simple table like the one below.