Identifying search terms (concepts and synonyms)

Once the question has been formulated using the PICO method, the next step involves identifying the words that will be used to find information. These are the foundation for your search. You can start your search strategy by keeping a record of significant words while doing background reading on the subject, or by using a thesaurus or dictionary.


Concepts are the main topics or headings that emerge from the question. Try to keep to a maximum of four or five concepts to avoid over-complicating the search.


Synonyms are alternative search terms for the same concept. Terms can vary between countries, for example: ‘Accident and Emergency’ in the UK has the same meaning as ‘Emergency Department’ in Australia. Synonyms are included under broad subject headings in sophisticated databases such as MEDLINE, Embase, or PsycINFO. Word spellings may also vary: ‘paediatrics’ in Australia is expressed as ‘pediatrics’ in the USA.

Let’s consider the PICO question: ‘Can brief intervention methods be used as an effective smoking cessation technique with teenagers?’ The following concepts and synonyms can be identified.

  P I O
Concepts Teenagers Brief Intervention Smoking Cessation
  • Adolescents
  • Young people
  • Brief advice
  • Brief counselling
  • Motivational interview
  • Stop smoking
  • Quit smoking

More examples

Developing concepts and synonyms from focused clinical questions

Question: Can Cognitive behavioural therapy improve self-esteem in patients with eating disorders?

  P I O
Concepts Eating disorders Cognitive behavioural therapy Outcome
  • Eating disorder(s)
  • Appetite disorder/s
  • Bulimia
  • Anorexia
  • Cognitive behavioural therapy/ies
  • CBT
  • Talking treatment/therapy
  • Self esteem
  • Self-worth
  • Self-regard
  • Self confidence

Question: In newborn babies, does a waterbirth increase the risk of morbidity or mortality?

  P I O
Concepts Newborn babies Waterbirth Morbidity or mortality
  • Babies
  • Neonates
  • Newborns
  • Infants
  • Water immersion
  • Underwater birth
  • Water birth
  • Death or illness
  • Adverse outcomes