Caffeine withdrawal syndrome may develop after the abrupt cessation of (or substantial reduction in) prolonged daily caffeine ingestion. Headache is the hallmark symptom of caffeine withdrawal. However, other symptoms of caffeine withdrawal can occur, such as drowsiness; depressed or otherwise negative mood; irritability; difficulty concentrating; and flu-like symptoms (nausea, vomiting, or muscle pain/stiffness).
Symptoms of caffeine withdrawal syndrome must cause a person significant distress or impairment in social, occupational, or other important areas of functioning. The symptoms must not be better explained as the result of another medical condition or mental disorder.
This post has been updated according to DSM-5 (2013); Diagnostic code: 292.0.
Though withdrawal from caffeine is now a recognized syndrome, “caffeine use disorder” (which requires additional symptoms due to a substance) is still not a recognized diagnosis at this time.
Grohol, J. (2014). Caffeine Withdrawal. Psych Central. Retrieved on July 7, 2015, from http://psychcentral.com/disorders/caffeine-withdrawal/