| I demonstrated the potential of aggregate search query surveillance both as a data stream to test a priori hypotheses and generate theory for mental health research. I estimated the Great Recession's impact on psychological distress in the United States, estimated seasonal variability in some common mental health problems in the United States and Australia, and synthesized the potential for aggregate search query surveillance in health behavior and chronic disease research, where these approaches have been limitedly applied.;The Great Recession appears to have negatively impacted the mental health of Americans. For example, a one-percent increase in mortgage delinquencies and foreclosures was associated with a 16% (95%CI, 9 to 24) increase psychological distress related queries one-month and 11% (95%CI, 3 to 18) four-months later, in reference to a pre-Great Recession mean. Mental health problem queries may follow consistent seasonal patterns, declining in the summer. Monthly mental health search trends were monitored for 2005-2010. There were more than 10 million queries per month for mental health problems in the United States. Queries typically declined 15% (standard deviation [SD], 10) during the summer months for both (June, July, and August) the United States and (December, January, February) Australia. Patterns were consistent for "anxiety", "bipolar", obsessive compulsive disorder ("OCD"), "depression", "suicide", attention deficit-hyperactivity disorder ("ADHD"), "eating disorder" and "schizophrenia" queries.;Aggregate Internet search query surveillance is a low-cost method for mental health surveillance and investigation. In principle, the methods used in both empirical reports are generalizable to other health outcomes manifested on Internet search engines. |
