Cochrane systematic reviews and those systematic reviews considering interventions often include a filter to restrict the results to studies reporting Randomised Controlled Trials (RCTs). Consider whether you wish to include a filter for a particular type of study design as part of your search strategy. These exist for RCTs but also for other study types including Observational Studies and Patient Issues. For more information about where to source standardised, pre-tested search filter search strategies optimised for different databases which you can copy and paste and add to your own search strategy see the Using Filters tab of this guide.
Antidepressant drugs OR antidepressive agents
Eating disorders AND cognitive therapy
AND and OR are Boolean operators.
OR is used to combine synonyms, abbreviations and all related terms on a similar concept. You can OR together subject headings for a particular concept with relevant keyword searches. 'OR is more'. Your result set will get larger as you OR together more terms.
AND is used (normally at the end of the search) to combine together different concepts and to retrieve results where all the concepts are present. AND narrows down your results and makes your search more specific. AND is sometimes automatic for two or more search terms depending on the database.
Focus (in the Ovid databases):
It is possible to both Explode and Focus a subject heading search.
A search on Embase on the Ovid platform showing the initial Subject Heading selection screen. Explode and Focus are available to select:
By clicking on a specific Subject Heading in the list, e.g. antibiotic agent, you enter the thesaurus and can see what the term is used for, the broader terms and narrower terms. By selecting Explode for antibiotic agent in Embase you will automatically retrieve articles which have also been tagged with all of the narrower more specific named antibiotics.
Below you can see the Full Record for a particular article (in Embase on the Ovid platform) with the Subject Headings listed which have been used to tag this particular article. You can see that 'penicillin allergy' is one of the subject headings assigned to this article and the asterisk * before the subject heading indicates that this was deemed to be key to what the article was about when it was added to the database and subject headings assigned. A normal subject heading search for 'penicillin allergy' or its exploded broader term would retrieve this article but so would a focussed search *penicillin allergy/. An exploded and focused search for the broader term, e.g. drug hypersensitivity, would also retrieve this article - exp *drug hypersensitivity/.
It is always worth checking to see whether any systematic reviews which have a concept in common with your search question have published their search strategy. If they have then this will act as a useful starting point for you to use for your search. Remember it is not necessary for all the concepts of the systematic review to be the same as you should be able to isolate the specific lines of the search strategy relevant to you. So for example if I am undertaking a systematic review on the 'effectiveness of phototherapy for neonatal jaundice' I may find that part of a search strategy for a published review on 'Phototherapy for treating pressure ulcers' is very relevant for me. I will then need to either create a search strategy element for my other concept of 'neonatal jaundice' or locate another systematic review which may have already created a search strategy including an element for this concept, e.g. one on 'Early intravenous nutrition for the prevention of neonatal jaundice'.
Below is an excerpt from a published Cochrane systematic review on 'Phototherapy for treating pressure ulcers' showing the search lines for the phototherapy concept (optimised for Ovid Medline) which could then be used in a different search and combined with other concepts.
Systematic reviews in the Cochrane Library should all publish their search strategies and in many cases will show the search strategy they used for each database they searched (optimised for each database) - this normally appears in the Appendix of the full text for a Cochrane review.
The PRISMA 2020 checklist states for '#7 Search strategy' that you should "Present the full search strategies for all databases, registers and websites, including any filters and limits used". The 2021 PRISMA searching extension increases that to "Include the search strategies for each database and information source, copied and pasted exactly as run". However, unfortunately you may find that older systematic reviews and even some current ones may not do this. Note too that in some cases the full search strategy may appear as a supporting document on a journal site as opposed to forming part of the pdf of the article.
Pay attention when looking to use a published search strategy to both the database and the platform it is hosted on and for which the search strategy has been optimised. If you are searching the same database on the same platform then you should simply be able to copy and paste the search strategy in to generate results. If you are uncertain about what the lines of the search strategy mean and what they are searching, e.g. exp, adj or .tw then see the information on the Advanced search techniques tab.
Remember when using a search strategy from another systematic review that you should assess it for quality rather than simply copying it in. Are there any other search terms that should be included, have they located all appropriate subject headings, and so on? See the information about PRESS: Peer Review of Electronic Search Strategies on the Advanced search techniques tab. The age of the source systematic review is also important as subject headings change to reflect changes in medical science. As such if you are working in an area of rapid development and the strategy is a few years old you may wish to just use it as a starting point rather than directly copying.
Finally if you do use all or part of another's search strategy then do remember to acknowledge the source.