There are four caffeine-induced psychiatric disorders recognized by the DSM-IV, the diagnosis manual of the American Psychiatric Association: caffeine intoxication, caffeine-induced anxiety disorder, caffeine-induced sleep disorder, and caffeine-related disorder not otherwise specified.

And, as you know if you have ever had to walk low-Starbucks-density wastelands, withdrawal can result in nausea, lethargy and depression. But what of the classic, washed-up-child-star-style overdose?

The Mallinckrodt Baker Material Safety Data Sheet describes the lethal dose of caffeine as 192mg/kg in rats (note: does this imply study of multiple-kilogram rats? Potentially capybaras? Maybe Norwegian browns from the Bronx?).

In humans, lethal toxicity is estimated at between 150 and 200 mg/kg, meaning that an average adult would have to consume between 80 and 100 cups of coffee in a very short period of time to induce extreme badness.

Forensic Science International reports a couple deaths from caffeine toxicity, all resulting from overdose of caffeine pills.

The moral seems clear: once you reach your 70th cup of the afternoon, consider switching to Benzedrine, methamphetamines or another similar stimulant.

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