Accuracy of geographically targeted internet advertisements on Google AdWords for recruitment in a randomized trial.

Posted: Jan 17, 2013
J Med Internet Res. 14. 3. e84.
KEYWORDS: International, Web, Non-Cancer


Web-based recruitment using targeted ads based on Google search terms is a feasible strategy.

Why this item may be useful

The authors set out to evaluate the usefulness of Goggle AdWords in recruiting patients for a clustered randomized trial using online cognitive behavior therapy for treatment of depression. The cluster study design required that patients and controls be recruited in widely separated geographic areas. The investigators purchased Google ads and indicated the geographic areas (defined by postal code) in which the ads should be displayed when depression-related terms were searched by Google users. The ads directed interested individuals to visit the study website and complete a questionnaire. Findings indicated that there was very little contamination of the control areas. Ninety-five percent of visits to the website resulted from AdWords advertisements. The cost of this strategy was less than that of other methods of raising awareness.


  • This study was conducted in the United Kingdom.
  • Adwords provide the option of purchasing sponsored links that become visible when certain key words are targeted; they can be purchased to be targeted by location.
  • Google Analytics was used to evaluate the accuracy of targeting the ads. Better coordination between AdWords and Analytics would make this type of recruitment easier.
  • Study noted that increasing use of mobile access to the web in encouraging the use of location-specific ads but concerns about privacy have resulted in Google allowing peopel to opt out of its location service,  In this study, 12% of visits were from mobile devices.  It is possible that as this proportion increases, geo-locating users may become more difficult.
  • Geotargeting strategies with internet and social media technologies should be taken into consideration when planning relevant studies.