Lead investigator John W. Ayers of the Graduate School of Public Health at San Diego State University said telephone surveys are used to try to glimpse inside the minds of respondents, but this approach is limited because respondents may be reluctant to honestly discuss their mental health. Surveys are also expensive so there is a lack of data, Ayers said.
"The Internet is a game changer," Ayers said in a statement. "By passively monitoring how individuals search online we can figuratively look inside the heads of searchers to understand population mental health patterns."
Using Google's public database of queries, the study team identified and monitored mental health queries in the United States and Australia for 2006-10.
All queries relating to mental health were captured and then grouped by type of mental illness, including attention-deficit/hyperactivity disorder, anxiety, bipolar, depression, eating disorders including anorexia or bulimia, obsessive compulsive disorder, schizophrenia and suicide.
The study, published in the American Journal of Preventive Medicine, found all mental health queries in both countries were consistently higher in winter than summer.
For example, research showed eating disorder searches were down 37 percent in summers versus winters in the United States and 42 percent in summers in Australia, while schizophrenia searches decreased 37 percent during U.S. summers and 36 percent in Australia.