Are caffeinated beverages like coffee magical for fighting the symptoms of sleepiness, or are they evil for interfering with sleep and triggering symptoms commonly associated with anxiety disorders? The answer to both questions is a resounding yes!

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Photo Credit: Susanne Nilsson | CC BY-SA 2.0

At Boing Boing, Murray Carpenter has written a sweeping long read about our love-hate relationship with caffeine. The world's most popular psychoactive substance, caffeine is used daily by untold numbers of people to stave off sleepiness and boost alertness throughout the day. But caffeine's stimulative perks are almost certainly diabolically and perniciously linked to the fuzzy-headedness and chronic lethargy so many of us use them to confront in the first place. "It is a fantastic drug for treating the symptom of sleepiness," writes Carpenter, "but it can lead to increased sleepiness by interfering with sleep."

Carpenter highlights a number of recent investigations into caffeine's disreputable qualities in the course of the feature, but two publications, in particular, caught my eye. Carpenter writes:

A team of California scientists found another variable in how caffeine affects sleep: chronotype. That term describes our time-of-day preferences. Some of us are morning people, often known as larks, while others are evening people, better known as owls. In a study of fifty university students consuming caffeine at will, who used wrist-activated motion detectors and sleep logs, the scientists found that morning people were most susceptible to caffeine's sleep-disrupting effects. They noted that the findings were limited by the group – all university students, mostly sleep deprived, and with relatively few morning people among them. Still, their 2012 paper was the first to report a possible association between chronotype and caffeine's effects on sleep quality, suggesting there is plenty of room for more research.

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Chronotypes are a fascinating area of investigation in sleep research, with increasingly recognized implications for everything from napping strategies to what time of day students should start school. Personally, I'm a lark. In my experience, a coffee taken any time past noon usually translates to difficulty sleeping later. I suppose it makes sense that people with different chronotypes would respond by degrees to caffeine's sleep-disrupting effects, but it's a connection I'd never made before reading this.

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Carpenter continues:

Even though virtually all of us are aware of caffeine's effects on sleep, we often don't fully appreciate them. That is the message from a 2008 review of caffeine and daytime sleepiness. Authors Timothy Roehrs and Thomas Roth said that caffeine does not affect REM sleep, as other stimulants do, but decreases stages three and four sleep, which account for about 20 percent of our sleeping time and include some of our most restful, restorative sleep. "The risks to sleep and alertness of regular caffeine use are greatly underestimated by both the general population and physicians," they concluded. Again, there's that caffeine conundrum – should we use it to fight daytime fatigue or do without and see if our energy levels improve?

Research has shown that we are terrible judges of how tired we actually are. That experts also suspect we are underestimating the risks to sleep of regular caffeine use, then, is particularly worrisome. Add it to the long list of reasons it's impossible to get out of bed in the morning, I guess.

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Check out the rest of Carpenter's piece on how caffeine messes with our heads, at Boing Boing.