The Archives of Internal Medicine recently released a study that linked reduced incidence of depression with increased coffee consumption. While the actual study only touted an "association" between coffee consumption and reduced rates of depression, the popular media took the ball and ran with these findings to present a different picture to the general public.
The headline for the link for the story on Boston.com read "Can Woman Avoid Depression by drinking Coffee?" This headline is emblematic of a long standing trend in the popular media to categorize medical research in a way that is misleading to those without medical expertise. Of course the headline isn't entirely unreasonable but to most people who merely glance at it or perhaps read a few paragraphs the message may well be "Avoid Depression" and "Drink Coffee" but this is not exactly what the study says.
In very plain English the message of the study is "We observed a group of woman and those who developed depression reported that they drank more coffee than those that did not." If you don't have a backround in science it is easy to get from that the message that "Coffee protects against depression.". Yet the difference between these ideas is subtle but critical.
It is presumptious to infer that coffee can protect against depression based on the results of this study because we don't fully understand the nature and direction of the association. The fact is the study does not offer concrete evidence into the observed relationship between coffee and depression. We can only say that for some as of yet unexplained reason, people who drink more coffee seem to have less depression than those who drink less coffee.
For all we know the association could be that coffee shops tend to be located near psychiatrists offices and people who seek psychiatric care (and therefore areless likely to develop depression) also just happen to stop for coffee when they visit their psychiatrists. It could be that people who can afford coffee come from a higher socioeconomic status or have access to better preventive treatments for depression.
Of course these explanations are somewhat ridiculous (especially considering that medical treatments for depression have questionable efficacy) but the point is clear: there are many explanations possible that could account for this association besides concluding that coffee protects against depression. For all we know coffee may actually even cause depression.
A more realistic potential snag in this study that I see is that caffeine use is not generally recommended in two important groups of people that have high rates of depression as compared to the general public. People with sleep disorders and people with anxiety disorders can not drink coffee and are told by doctors to avoid them because they worsen anxiety and insomnia symptoms. These groups also have higher a incidence of depression than the general population.
The study authors agreed with this and even commented in the article on this possibility saying "caffeine might induce sleep disturbances or insomnia or anxiogenic effects. It is possible that sleep sensitive or anxious woman are aware of the stimulatory effects and may lower their consumption accordingly." While the study did include asking the subjects to complete an index assessing mental health, it did not gather data on anxiety disorders or sleep disorders that could be controlled for in the final results.
The headline for the link for the story on Boston.com read "Can Woman Avoid Depression by drinking Coffee?" This headline is emblematic of a long standing trend in the popular media to categorize medical research in a way that is misleading to those without medical expertise. Of course the headline isn't entirely unreasonable but to most people who merely glance at it or perhaps read a few paragraphs the message may well be "Avoid Depression" and "Drink Coffee" but this is not exactly what the study says.
In very plain English the message of the study is "We observed a group of woman and those who developed depression reported that they drank more coffee than those that did not." If you don't have a backround in science it is easy to get from that the message that "Coffee protects against depression.". Yet the difference between these ideas is subtle but critical.
It is presumptious to infer that coffee can protect against depression based on the results of this study because we don't fully understand the nature and direction of the association. The fact is the study does not offer concrete evidence into the observed relationship between coffee and depression. We can only say that for some as of yet unexplained reason, people who drink more coffee seem to have less depression than those who drink less coffee.
For all we know the association could be that coffee shops tend to be located near psychiatrists offices and people who seek psychiatric care (and therefore areless likely to develop depression) also just happen to stop for coffee when they visit their psychiatrists. It could be that people who can afford coffee come from a higher socioeconomic status or have access to better preventive treatments for depression.
Of course these explanations are somewhat ridiculous (especially considering that medical treatments for depression have questionable efficacy) but the point is clear: there are many explanations possible that could account for this association besides concluding that coffee protects against depression. For all we know coffee may actually even cause depression.
A more realistic potential snag in this study that I see is that caffeine use is not generally recommended in two important groups of people that have high rates of depression as compared to the general public. People with sleep disorders and people with anxiety disorders can not drink coffee and are told by doctors to avoid them because they worsen anxiety and insomnia symptoms. These groups also have higher a incidence of depression than the general population.
The study authors agreed with this and even commented in the article on this possibility saying "caffeine might induce sleep disturbances or insomnia or anxiogenic effects. It is possible that sleep sensitive or anxious woman are aware of the stimulatory effects and may lower their consumption accordingly." While the study did include asking the subjects to complete an index assessing mental health, it did not gather data on anxiety disorders or sleep disorders that could be controlled for in the final results.
So is the effect we see in these findings really that drinking coffee caused a reduced chance of developing depression or was it that people with other medical problems strongly associated with depression also tended to avoid coffee because it would exacerbate their symptoms of anxiety and insomnia? Or is it something else? We simply don't know.
In the past some of our best medical discoveries have come from observations such as this association. But this method has also created some of our most massive medical blunders (ever read the story of hormone replacement therapy?). Individuals should continue to be skeptical of how findings of medical evidence are presented in the popular media.
The reasonable conclusion from this study is that coffee is probably not harmful to humans and may indeed have health benefits so if one enjoys coffee they should continue to enjoy it in moderation. We can also say that coffee is associated for an unknown reason with reduced risk of developing depression, that this effect could be real but it could also be artificat (we don't know). We can definitvely say that coffee will definitely make symptoms of sleep disturbances and anxiety, often found in depressed individuals, much worse.
The take home message is that if you are interested in preventing depression you may want to hold off on buying that big bag of coffee beans, especially if you have trouble sleeping or are anxious, until further studies can be done to to explain the true nature of this association. The real danger of how studies like this are reported is it may cause someone with anxiety or insomnia, in addition to depression, to binge on coffee thereby making their anxiety/insomnia symptoms worse and that is definitely not the right thing to do in this situation.
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