A new study using the patterns of Google search queries suggests that mental illnesses flourish in winter and decline in summer.
In both the United States and Australia, researchers found distinct seasonal patterns, high in winter and low in summer, in searches pertaining to anxiety, obsessive compulsive disorder, bipolar disorder, eating disorders, depression, suicide, attention deficit hyperactivity disorder and schizophrenia. The study appears in the May issue of The American Journal of Preventive Medicine.
Searches related to eating disorders varied the most — 37 percent higher in winter than summer in the United States and 42 percent higher in Australia. The smallest variations were in searches related to anxiety: 7 percent and 15 percent more common in winter than summer in the United States and Australia, respectively. The variations persisted after the researchers controlled for seasonal differences in Internet use, mentions of the diseases in news articles and other factors.
Why this happens, and whether it is connected to increased incidence, is unclear, but it is known that varying hours of daylight, variations in physical activity and seasonal changes in blood levels of vitamin D and omega-3 fatty acids can affect mood.
“We have new kinds of data with which we can start to think about seasonality,” said the lead author, John W. Ayers, a research professor at San Diego State University. “This is just the beginning of a new research agenda.”