Is Summer the Sanest Season?

What Google searches tell us about the seasonality of mental illness.
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Searching for mental illness. (SCREENSHOT)

Searching for mental illness. (SCREENSHOT)

Spring has sprung, at least for most of us, which means sundresses, seersucker, and boozy croquet parties on the front lawn. Goodbye happy lamp, hello mimosa.

But it’s not just champagne that’s lifting our spirits and banishing the wintertime blues. According to Google (and a team of researchers from the University of Southern California, Harvard, and Johns Hopkins) mental illnesses—such as obsessive compulsive disorder, depression, and anorexia—are far more seasonal than we think.

The epidemiologists, led by John Ayers, combed through every Google search performed in the United States and Australia between 2006 and 2010, looking for queries like “symptoms of” and “medications for” OCD, anxiety, ADHD, bipolar, depression, anorexia, bulimia, and schizophrenia.

It’s not just champagne that’s lifting our spirits and banishing the wintertime blues.

The Internet, the authors note in a studyforthcoming in the American Journal of Preventive Medicine (PDF), is “the world’s most relied-on health resource. Because of mental health’s complexity, stigma, and obstacles to care, patients are likely to investigate their problems online.” At the same time, tracking a population’s long-term mental health indicators is difficult for epidemiologists; phone surveys are often unreliable—would you want to discuss the voices in your head with a complete stranger?—and cost prohibitive. Google queries, on the other hand, are nakedly honest and free to collect.

“This is Moneyball for mental health,” Ayers told me. “Big data and hypotheses-free investigations will allow for an unprecedented growth of knowledge across disciplines, especially mental health.”

If, as the researchers suspected, mental illness has a seasonal component, monthly dips and peaks in American self-help searches should be inverted from Australian ones, where winter arrives in March and lasts through September.

Indeed, that’s just what they found. Overall, American mental illness queries rose 14 percent in January while Australia’s 11 percent uptick came six months later (in July).

Upon closer inspection, certain disorders appeared to be particularly season-dependent. Queries involving “anorexia” and “bulimia,” for instance, were 37 percent higher in winter than in summer; schizophrenia-related searches took an equal jump, while ADHD searches climbed 31 percent. “Anxiety,” on the other hand, only appeared slightly more frequently in colder months than in warmer ones.

“We were very surprised to find that this seasonal pattern was replicated across a number of disease categories,” Ayers said. “For example, we saw strong seasonal patterns for schizophrenia, a disease for which symptom severity had not been associated with seasonal patterns, no doubt in part due to the challenges of performing field surveys of individuals with psychotic symptoms.”

The researchers propose several mechanisms that might make mental illness more seasonal than previously thought.

Daylight, certainly, has an impact on our circadian rhythm and has long been implicated in wintertime affective disorders. Vitamin D deficiency, too, may play a part, as a lack of sunshine decreases the body’s ability to absorb the nutrient. Summer, meanwhile, brings an increase in omega-3 consumption—thought by some physicians to promote mental wellness—as well as an obvious social benefit: long, warm evenings to go for jogs, play in the garden, and share a beer with the neighbors.

“There is a lot more we need to learn about mental health and seasonality,” Ayers said. “For instance, is there a universal mechanism that impacts our mental health? We don’t know, but our data suggest looking is an excellent idea.”

Google can’t answer such questions, of course—even if it appears to know us better than we know ourselves. The “why” of mental illness, being a uniquely human condition, is a human one to solve.

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