Psychiatrist Emily Deans: Coffee May Keep You From Suicide
I just love psychiatrist Emily Deans. Here's another great blog post by her on Psychology Today on how coffee may be protective against suicide:

A recent study done by the Harvard School of Public Health analyzed the coffee-drinking habits of over 208,000 people over decades. In the time frame of the study, 277 of those people died by suicide. Interestingly, those people who drank 2-4 cups of coffee a day had a 50% lower risk of death by suicide. The researchers thought caffeine might be the player here, as caffeine has chemical activity that not only increases alertness (as we well know) but also has some antidepressant effects. The data is consistent with a bunch of previous studies over the years.

This last bit is important. An epidemiologist who encourages me to be skeptical in scientifically solid ways in reading studies has coached me to look for a body of work on a topic, not just go by a single study.

Deans later very clearly explains some of the problems with the "science" you see in mainstream media -- referencing cohort studies like they mean something, when they're really, as I call them, "leaps to conclusions after the fact." In Deans' words:

The limitations of these studies are profound. They are observational and tell us nothing about cause and effect (we can only guess at that). For those reasons, when large observational studies tell me that moderate exercise or fish or oatmeal is good for me, I yawn.

We've all been told that these things are good for us by the health authorities for the past gazillion years. Healthy people with adequate impulse control and executive planning capabilities will therefore adjust their lives to eat more fish and get some exercise. They are also far more likely to not drink heavily, not smoke, and get the appropriate amount of sleep etc. etc. etc. And while the epidemiologists say they can pick apart all these variables if they ask the right questions and use the right computer program to take out one variable, I'm skeptical.

But the same limitations that plague the results of these large observational studies that seem to form the backbone of public health advice these days is actually a strength of the coffee study. Coffee consumption is not one of those healthy things we've been told to do. In fact, we are typically told to limit caffeine, because it can make you anxious and irritable and wreck your sleep. So the coffee drinkers are not typically the magical healthy cohort of people who all drink green smoothies and eat lentil soup. In fact, coffee drinkers are more likely to smoke, drink, get poor sleep, and don't exercise as much as those who don't drink coffee. Therefore finding that coffee drinking is associated with less depression and less completed suicide even though coffee drinkers tend to have less healthy habits in general is very interesting.