What sort of psychological disorder or drug addiction/withdrawal leads to unreasonable anger in people?

Many disorders: Many psychological disorders can have anger as a symptom. Careful evaluation is needed. For instance bipolar disorder and add can both have anger manifestation but are treated with very different medications. Most additive drugs can cause anger during the withdrawal period and thus slow .Withdrawal is needed.

Anger and drugs: Your question is a very broad one. Anger is one of several innate emotions ; we all have it . It can obviously be made worse by all kinds of problems and basically any psychological problem can manifest itself in some increased anger. Anger also almost always masks shame. There is always shame involved in drug use.