I doubt it's a full on physical addiction but you may have some kind of psychological dependency forming. Melatonin will mess with your hormones - it causes testosterone levels to lower, which can cause erectile issues in males and estrogen/testosterone imbalances in women with prolonged use. It's fine to use once in a while but I would caution against using it regularly. When I stopped using melatonin I switched to Valerian and Kava Kava (both available in tea form or in supplement form) for my sleep issues and anxiety.