From Sacramento Lawyer:
Persistent and recurrent maladaptive gambling behavior may be indicate by five or more of the following criteria. The problem gambler:
1. Is preoccupied with gambling (e.g. reliving past gambling experiences, handicapping or planning the next venture, thinking of ways to get money for gambling)
2. Needs to gamble with increasing amounts of money in order to achieve the desired excitement
3. Has repeated, unsuccessful efforts to control, cut back, or stop gambling
4. Is restless or irritable when attempting to cut down on or stop gambling
5. Gambles to escape from problems or relieve feelings of helplessness, guilt, anxiety, or depression
6. After losing money gambling, often returns another day to get even (i.e. "chasing" one's losses, etc.)
7. Lies to family members, therapists, or others to conceal the extent of involvment with gambling
8. Has committed illegal acts, such as forgery, fraud, theft, or embezzlement, to finance gambling
9. Has jeopardized/lost relationships, jobs, or educational/career opportunity because of gambling
10. Relies on others for money to relieve a desperate financial situation caused by gambling.
I think you could pretty much replace "gambling" with any addictive activity, be it drugs, alcohol, etc.
Well, after reading that, it sure makes me want to go to Las Vegas in two days!