Go a few hours without the regular dose of caffeine, get a headache. It's a common problem we jokingly call caffeine withdrawal, but there's mounting evidence that that withdrawal, as well as caffeine intoxication, are genuine medical conditions deserving of diagnosis.
According to The Wall Street Journal, "the latest version of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, commonly referred to as DSM-5, includes both caffeine intoxication and withdrawal. These conditions are considered mental disorders when they impair a person's ability to function in daily life."
Until recently, caffeine withdrawal was classified as a "research diagnosis." Now it's been upgraded. The Journal writes there's some controversy around the decision, since caffeine withdrawal and intoxication rarely cause serious impairment. In fact, the average person suffering headaches after 12 hours with no coffee doesn't necessarily fit the mental disorder status.
To be diagnosed with caffeine withdrawal, a patient must experience at least three of five symptoms within 24 hours of stopping or reducing caffeine intake: headache, fatigue or drowsiness, depressed mood or irritability, difficulty concentrating, and flulike symptoms such as nausea or muscle pain," writes the Journal. But there's an added requirement: those conditions must cause "clinically significant distress or impairment."
The variation in coffee intoxication is even more interesting. Some people can suffer coffee intoxication by ingesting 250 milligrams of caffeine, while others have to ingest much higher doses. Similarly, some people metabolize caffeine quickly enough to rid the body of half a dose in two hours; for others, it can take up to eight.
There's some bad news for people genuinely going through caffeine withdrawal, too--slowly cutting back isn't guaranteed to avoid the symptoms of withdrawal. Going cold turkey is tough, but most symptoms should disappear after a week. The Journal quotes experts who recommend drinking no more than 100 milligrams of coffee at a time, and doing that on an irregular schedule. In the long run, that could help avoid both intoxication and withdrawal, and make caffeine more effective when you really need it.