Koff is correct:

addiction  is a pattern of compulsive drug use which is characterised by a craving for drugs - generally opiods - for effects other than pain relief. Sudden withdrawal of the drug leads to severe physical effects, but this is an effect of the drug, not the addiction. Even non-addicted people may suffer withdrawal effects to a minor degree.

dependence is more of a psychological state, in which one is given up to a habit, especially a strong dependence on a drug.

 Confusing, and almost - but not quite - synonymous. It may perhaps be explained in terms of cigarette smokers; they are dependent on the habit of smoking, but addicted to the nicotine.