Animal Study Suggests Cellular Clues to Cocaine Addiction / Join Together, 1 August 2008
http://www.jointogether.org/news/research/summaries/2008/animal-study-suggests.html
"According to a new animal study, active choice may play an important role in resumption of cocaine use long after periods of abstinence, suggesting that the pharmacological effects of a drug alone may not be enough to explain the phenomena of addiction and relapse."