The late afternoon cup of coffee with friends takes some time to leave your body. As much as 25 percent of your eight in morning coffee will still be in your body twelve hours later. Any amount of caffeine remaining in your system will result in reduced REM sleep, the deep sleep the body needs to rejuvenate. Studies at Wayne State University, published in Journal of Clinical Sleep Medicine, showed how drinking coffee on the way back from work impaired sleep quality. Caffeine taken six hours before sleep reduced sleep by at least one hour.
Symptoms of withdrawal
The afternoon drop in energy could reflect the coming off caffeinated high. At John’s Hopkins Medical School, researchers suggested that energy a person gets from morning cup of coffee is the result of reversing temporarily the symptoms of caffeine withdrawal. Moreover, researchers noticed that improvements in performance based on drinking coffee cannot occur without caffeine withdrawal first, suggesting that cognitive performance decreases and mood gets worse during the day as caffeine leaves the body, and the only way to get back to feeling “normal” is to drink more caffeine.
Reduce objectivity in decision-making
As caffeine triggers the release of adrenaline, the hormone stimulating a fast response, the fight-or-flight mechanism is extremely useful when one faces a danger, but not when the person needs to reply to a rather abrupt email from an angry customer. Increased adrenaline puts the brain in a state of hyper-alertness, a situation that promotes circumventing rational thinking in favor of a fast response.
When a person feels stressed all the time, a likely culprit is the caffeine habit. A 2002 study conducted by researchers at Duke University Medical Center showed that caffeine elevated the stress level in people who use it every day. The effects of caffeine taken in the morning persisted until bedtime, amplifying the stress consistently during the day.