alt Hacker NewsThis is the example I'm shocked more people don't invoke in these discussions. Gambling addiction is indisputably real, and slot machines (or craps tables or the ponies down at the track) don't even have stick a needle in you to get you hooked. Actions and reactions are more than enough.
Compulsive overeating relies on the same behavioral/reward mechanisms, with the added bonus of food being something you do physically ingest in the process.
Gambling addiction also has the highest suicide rate among addictions, so definitely serious. The Atlantic had an article recently arguing that allowing sport gambling in the USA was a mistake, imposing huge costs on the most vulnerable.