DSM-IV-TR specifies four caffeine-related disorders

In the clinician’s handbook for diagnosing mental disorders (the Diagnostic and Statistical Manual of Mental Disorders , known as the DSM-IV-TR ), caffeine-related disorders are classified under the rubric of substance-related disorders. DSM-IV-TR specifies four caffeine-related disorders: caffeine intoxication, caffeine-induced anxiety disorder, caffeine-induced sleep disorder, and caffeine related disorder not otherwise specified. A fifth, caffeine withdrawal, is listed under the heading of “Criteria Sets and Axes Provided for Further Study.”

Caffeine can produce a range of physical symptoms following ingestion of as little as 100 mg, although amounts of 250 mg or higher are usually needed to produce symptoms that meet the criteria of caffeine intoxication.

Caffeine intoxication

To meet DSM-IV-TR criteria for caffeine intoxication, a person must develop five or more of the twelve symptoms listed below; the symptoms must cause significant distress or impair the person’s social or occupational functioning; and the symptoms must not be caused by a medical disorder or better accounted for by an anxiety disorder or other mental disorder.

Because people develop tolerance to caffeine fairly quickly with habitual use, caffeine intoxication is most likely to occur in those who consume caffeine infrequently or who have recently increased their intake significantly.

Caffeine-induced anxiety and sleep disorders

DSM-IV-TR criteria for caffeine-induced anxiety and sleep disorders specify that the symptoms of anxiety and insomnia respectively must be more severe than the symptoms associated with caffeine intoxication. In addition, the anxiety or insomnia must be severe enough to require separate clinical attention.

The symptoms of caffeine intoxication include:
flushed face
diuresis (increased urinary output)
gastrointestinal disturbance
muscle twitching
talking or thinking in a rambling manner
tachycardia (speeded-up heartbeat) or disturbances of heart rhythm
periods of inexhaustibility
psychomotor agitation

People have reported ringing in the ears or seeing flashes of light at doses of caffeine above 250 mg. Profuse sweating and diarrhea have also been reported. Doses of caffeine higher than 10 g may produce respiratory failure, seizures , and eventually death.