The source said Spitzer -- who resigned Monday after he was found to have visited a $4,300-a-night prostitute in February -- has begun therapy since leaving office to explore, among a number of issues, whether he is addicted to sex, the New York Post reported Friday.

Experts said Spitzer's prostitute habits, which stretch back nearly a decade, may be a sign of sexual addiction.

"If it becomes an overwhelming urge to the detriment of your professional and familial relationships -- if it starts to screw up your life -- that is addictive behavior," said Dr. Jeffrey Gardere, a clinical psychologist. "Someone who displays this sort of behavior could be classified as having a sexual addiction."