Troubles from it
Similarly to other addictions, you have it if you do it instead of doing other important things, if you think about it all the time, if you cannot stop doing it even though you realize it is detrimental.
, etc etc. Also, by the way, you have withdrawals from not using it. Withdrawals can be classical, or just insomnia
, etc. If you feel better after doing heroin - you are also addicted.