2.7 Using Subject Headings
Why use both subject headings and synonyms?
In short - they cover each other's weak points. One of the strengths of subject headings, is they help account for language variation.
e.g. Articles where authors have used the terms malnutrition, malnourishment, or under nutrition will be tagged with Malnutrition/
However subject headings take time to be added to the thesaurus and applied to articles, so new articles won’t be tagged with subject headings just yet. Emerging topics and concepts will not have subject headings available to describe them. In both scenarios, you will instead be relying on your keywords to pick up these articles. However, keywords only retrieve that exact term so you need to think of a variety of synonyms to ensure you’re getting all relevant articles.
This is why subject headings are useful – because they account for language variation! Using both ensures your search is picking up all possible articles of interest.
Finding subject headings in databases
In every database that uses subject headings, there will be a way for the database to suggest subject headings for you. Look out for the 'map term to subject heading' or 'suggest subject terms' checkbox.
For example, in Medline it works like this:
Once you have all your subject headings, you can add them to your search term table (also known as a concept table) to keep track of them and guide your database searching.
Here is what that might look like using the same example from previous modules.
| Concept: Diabetes | Concept: Glucose-lowering drugs | Concept: Dietary supplements |
|---|---|---|
| Gestational Diabetes | Hypoglycemic Agent* | Diet* supplements |
| Diabetes during pregnancy | Hypoglycemic Drug | Food Supplement* |
| Antidiabetic agent | Herbal Supplement* | |
| Diabetes, Gestational (MeSH) | Antihyperglycemic | Neutraceutical* |
| Nutraceutical* | ||
| Hypoglycemic Agents (MeSH) | Nutriceutical* | |
| Dietary Supplements (MeSH) |
Hot Tips
- See subject headings in action in the next module!
- Subject Headings include a scope note which describes the definition of the Subject Heading. You can (and should!) read the scope note to make sure you are using the correct Subject Heading.
- Use the most specific subject headings you can find to describe your concepts - don't use ones that are too general.
- Subject Headings are different across databases. For example, the subject heading for postpartum depression may be 'Postnatal Depression' in Embase but is 'Depression, Postpartum' in Medline. This means every time you try a search in a new database, you need to find the right subject heading again.