Coffee and Suicide

Ichiro Kawachi, Walter Willett, Graham Colditz, Meir Stampfer, Frank Speizer, Arch Intern Med. 1996;156:521-525

Depressed? Feeling suicidal? Have two to three cups of coffee and live!

"Caffeine is the most widely consumed psychoactive substance in the world, about 75 percent being taken in the form of coffee. Caffeine acts principally as a central nervous system stimulant" say Harvard based researchers. These researchers believe so strongly in caffeine's power as a stimulant, they have reported that drinking 2-3 cups of coffee per day reduces the risk of suicide by 66 percent (Relative risk = 0.34; 95% C.I. 0.17 - 0.68).

But it's probably a little premature to build that coffee bar on the Golden Gate Bridge or your local Lover's Leap.

Biological plausibility. Sure, coffee is a pick-me-up. But is it enough of a pick-me-up to curb suicide? Unfortunately, no data to support this notion was presented. Coffee may improve mood and feelings of well-being, somewhat. But these effects are a far cry from preventing suicide.


Key ignored confounder. According to the researchers, "the lower risk of suicide among coffee drinkers may be spurious if health professionals advise depressed patients (particularly those taking psychoactive medication) to avoid caffeine, thereby raising risk in the non-coffee-drinking group. A limitation of the current study is that neither the prevalence of clinical depression nor the use of tricyclic antidepressant medication was ascertained in the cohort."


Effect of adjusting for confounders. The 0.34 relative risk calculation had a confidence interval that ranged from 0.17-0.68 when adjusted for age only. When adjusted for more potential confounding factors, including smoking, drinking and stress, the confidence interval widened to 0.14-0.87. The reported association was weakened when other factors that could have caused the association were considered. As discussed above, information on potentially important confounder was not available and considered in the analysis.

I was surprised that these researchers viewed caffeine in essentially the same light as amphetamines. They call it a "stimulant" and talk about cups of coffees as "doses." People who drink coffee "self-medicate." I wonder when they will start pushing the FDA to regulate caffeine?

Material presented on this home page constitutes opinion of the author.