Death by Cruise Ship, Lithium, and Suicide

Imagine that the Journal of Hypochondriacal Cardiology reported that the incidence of fatal strokes aboard cruise ships was five times the national average.  Should we conclude that the boat trips were killing passengers—and insist that Washington ban cruise ships?  Certainly not. Further investigation would probably reveal that the seafarers were comparatively old, and that they were not stroking out in greater numbers than were landlubbers of the same age.  The ships did not cause the deaths anymore than hospice centers kill people. Wherever old people congregate, one can expect deaths to be more prevalent than at places where younger people gather.


Mistaking correlation (ships and strokes) for causation (ships cause strokes) is an error in reasoning.  Jenny Listman, an anthropological geneticist at Yale, believes that the proponents of our first dangerous idea, Drug Our Drinking Water, are making the same kind of error. Bioethicist Jacob Appel cited two studies showing that the suicide rate was dramatically lower in places where the level of lithium in the water supply was naturally higher. In lower lithium areas in one of the studies, a third more people killed themselves.  And so Appel concluded that Washington, in the interest of saving 13,000 lives across the country, should perhaps spike all of our drinking water with lithium. 

Listman reviewed the two studies that Appel cited, and found methodological problems with the research. (You can read Listman's full analysis in the comment stream here.) She also cited work showing that in areas of high rainwater, lithium levels in drinking water were lower—presumably rain dilutes the lithium—and that suicide rates were higher in areas with heavy rain and lower where it's sunny.  In other words, it may be bad weather—not lithium—that's causally related to suicide.  Rather than drugging our drinking water, Washington might try to serve up a little more sunshine.

"Appel is an ethicist," Listman emailed me later, "and so is most concerned with the moral argument, and I was thinking after I posted my comment that I am entirely concerned with the scientific argument and was wondering if that means I'm insensitive. But I figure that there is no need to spend my energy on the moral argument if the science is invalid, and I can worry about the moral argument when it is relevant. It's also worth noting that I work in a psychiatric genetics lab group so I'm aware of the toll of mental illness on individuals as well as society."

When contacted by Big Think, Jacob Appel said he was "glad to respond to Jenny's thoughtful observations":

"As an ethicist, I am far more concerned with the morality of including beneficial additives to the drinking water than the specific benefits of any particular additive.  Whether or not lithium will prove beneficial, and whether the benefits, if they pan out, justify the cost, is an important question that should be explored further by epidemiologists and public health experts.  If it turns out that lithium does not indeed provide tangible benefits, then there would certainly be no purpose in adding it to the drinking water or consuming it in any other way.  Bioethicist Julian Savulescu has made a intriguing argument elsewhere that cognitive enhancement may be the next benefit provided by fluoride-like water treatments, another area certainly worth exploration.  So I am not wedded to lithium, per se, so much as the principle that using the drinking water to enhance public health is an idea that should be explored further and with an open mind.  I would also note that, if those who fear that trace amounts of drinking water were dangerous followed through on their arguments, they would campaign to have lithium removed from the water supply where it already naturally occurs."

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