The reaction that follows the ingestion of excessive caffeine, usually more than 250 mg. At least five of the following side effects are experienced: restlessness, nervousness, excitement, insomnia, flushed face, gastrointestinal disturbance, muscle twitching, diuresis, rambling flow of thought and speech, tachycardia or arrhythmia, and psychomotor agitation. Other physical or mental disorders such as anxiety disorder must be ruled out.