Controlled vocabulary is a standardized set of terms used by databases to describe and categorize articles based on their content. It works similarly to a unique hashtag for social media posts (e.g. #APHA2024 for the American Public Health Association 2024 meeting) or navigating through an online store's categories to get to a desired item (Clothing > Women's Clothing > Tops > Sweaters) rather than using the search box.
Using controlled vocabulary terms can return more relevant and specific results, and can help overcome variance in terminology, but you have to know where to find it and how to add it to your search. Different databases have their own controlled vocabularies:
Not all databases use controlled vocabulary; for example, Google Scholar and Scopus do not have their own controlled vocabulary. Searching with only controlled vocabulary may limit your results to just the articles that have been indexed - you may miss new articles or articles that are older than the controlled vocabulary term.
Here is a sample search in PubMed using just a few relevant MeSH terms for our research question:
Does the use of a mobile application improve medication adherence in older adults?
("Smartphone"[Mesh] OR "Mobile Applications"[Mesh]) AND "Medication Adherence"[Mesh] AND "Aged"[Mesh]