craving is part of addiction, anxiety of withdraw is addiction
that's not physical dependence
and I already admitted nicotine is physically dependent Heroin Addiction Effects: Physical Dependence and Tolerance Development
When the heroin has lost its effect the withdrawal symptoms show up: the user feels sick, sweaty and cold, has goose bumps, a running nose, stomach ache, and pain in arms and legs. Possible symptoms are vomiting and diarrhea. These symptoms disappear as soon as heroin is used again. That is how the user easily ends up in a vicious circle. Mental dependence means that the user anxiously wants to use the substance and doesn't feel comfortable without it anymore.