But overuse can develop into "caffeinism," which may cause muscle twitching, insomnia, headaches and heart palpitations.    From Wordnik.com.  [Cheat Sheet: The Dark Side of Caffeine] Reference

Caffeine is a drug that in large amounts, especially over an extended period of time, can lead to a condition termed "caffeinism.".    From Wordnik.com.  [Evil Caffeine!] Reference

Launched in 2002 by the Caffeine Awareness Alliance, the campaign calls attention to the risks associated with caffeinism and caffeine withdrawal syndrome, a disorder recognized by the psychiatric community.    From Wordnik.com.  [PR.com Press Releases] Reference