The Internet, it seems, can reflect the health of the body politic, though we may not like what we see. Consider, for instance, an analysis done by economist Seth Stephens-Davidowitz, as described by him in The New York Times earlier this month. More than 700,000 Google searches, he found, were performed last year by individuals seeking information on how to perform their own abortion. Some, he notes, used the phrase “how to have a miscarriage,” others inquired into the use of Vitamin C or bleach or a blow to the abdomen as an abortifacient, and a small minority queried the very words “how to do a coat hanger abortion.”

More disconcerting, however, are the trends he traces: those states with the highest frequency of these sorts of searches were (for the most part) the very same states that heavily restrict access to legal abortion. At the same time, he describes a sharp increase in such searches following 2011, a year when legal abortions began to be increasingly restricted in many places. Admittedly, he acknowledges, this is a preliminary analysis, deserving more academic study. Still, it suggests how this method of research can be used as a type of population-level microscope—in this case, so as to observe the alarming state of reproductive health care access in the United States.

This—the use of “big data” culled from the Internet for medical research—is the precise topic of a stimulating new book, Crowdsourced Health: How What You Do On the Internet Will Improve Medicine. It is written by Elad Yom-Tov, an academic who works from within the world of tech. Yom-Tov previously held positions in the research outfits of IBM and Yahoo, and is now a researcher at Microsoft. His book makes the case that what we divulge in cyberspace—whether through searches or posts on social media—constitutes an invaluable trove of data that can shed light on a wide range of medical issues. It’s a slim but effective volume, albeit more a description of his own research than a synthesis of the field. Nonetheless, it reveals both the promise and the pitfalls of such methods, and—just as notably—their potential perils.

At first blush, the overall premise seems sound. When medical illness—or, more commonly, apprehension thereof—strikes, the first place many (most?) of us turn is the Internet. Yom-Tov explores some of the reasons for this. Compared with a health care professional, for instance, the Internet is always available, has no other patients waiting, and—critically—permits a degree of anonymity when we are at our most vulnerable. (I can personally recall my first experience with this as a young teenager: a game of “spin-the-bottle” had me later neurotically combing the Internet for days on end in pursuit of definitive facts on the possibility of contracting HIV through kissing. For better or worse, it was many years before any similar concerns would be again raised).

CROWDSOURCED HEALTH: HOW WHAT YOU DO ON THE INTERNET WILL IMPROVE MEDICINE by Elad Yom-Tov The MIT Press, 160 pp., $24.95

Perhaps just as important, the Internet doesn’t charge copayments. Early in his book, Yom-Tov observes the role this factor plays when he looked at what people search for after they (or a relative) are given a diagnosis of cancer. “One of the terms that appear most often in queries in conjunction with different types of cancers,” he notes, “is ‘free.’” A cancer specialist tells him that this could be the result of people searching for “disease free survival,” a common metric of efficacy for cancer treatments. Alas, that was not the case: “[W]hen we looked at the queries closely,” he notes, “it became apparent that the context was ‘free diagnosis’ and ‘free treatment,’ probably because the people who submitted the queries had no other option for obtaining treatment.” As with Stephens-Davidowitz’s analysis, such a finding helps reveal the gaps within our health care system. Yom-Tov rightly points to uninsurance and underinsurance—serious and persistent deficiencies of the American health care system—as potential factors contributing to this phenomenon.