The authors followed 50,739 women (average 63yo) for 10 years in the Nurses' Health Study. All were depression-free at baseline in order to participate in this particular analysis. Coffee consumption was then evaluated as part of a validated food questionnaire every 4 years. Compared to those who drank less than a cup of coffee/week, those who drank 2-3 cups/d had 15% lower risk of depression while those who drank 4-5 cups/d had 20% lower risk. Those who drank decaffeinated coffee showed no association w/depression.
Coffee may prevent depression", this study really does nothing of the sort. In fact, as others noted, perhaps depressed women decided against drinking caffeinated coffee because too much caffeine makes them jittery & anxious and leads to insomnia. At the very least, we can be clear that it's probably not so much the coffee as much as it is the caffeine, which means that perhaps caffeinated tea and gasp! even soft drinks & energy shots, maybe even dark chocolate, might have a similar effect. I can't wait to see that research and how far the pendulum swings!
By the way, if you can remember back to last Friday's post regarding the link between depression and stroke, this study goes a long way towards explaining the link between coffee and stroke . . . Yes, it's tenuous at best, but still it's an interesting possibility!