Heroin: tolerance and dependence
There is evidence that after prolonged use heroin is highly addictive. People who use heroin regularly can develop dependence and tolerance to it, which means they need to take larger amounts of heroin to get the same effect.
Dependence on heroin can be psychological, physical, or both. People who are dependent on heroin find that using the drug becomes far more important than other activities in their life. They crave the drug and find it very difficult to stop using it.
People who are psychologically dependent on heroin may find they feel an urge to use it when they are in specific surroundings or socialising with friends.
Physical dependence occurs when a person's body adapts to heroin and gets used to functioning with the heroin present.