be addicted to, have a bad habit of...

はまる Obsessed with something. Usually used like this:はまっちゃった。   $$$
になる(くせになる) Have a bad habit – not like drugs but like biting one’s nails or saying “like” every other word.
やみつき やみつき:to get hooked on (verb form: やみつきになった!). Not a strongly negative word. . . you can use it like “He’s hooked on this video game” or “She’s hooked on this new pop star.”
(ちゅうどく) Hooked on drugs or gambling. The nuance is, the person is so hooked they can’t live a normal life – they lost their job or their marriage, etc.