Psychological Dependence refers to situations where there is no physical withdrawal, yet there is a compulsion to continue using a substance or carrying out an act. Sex “addiction” is a good example, as is the compulsion to eat sugar.
There is a wide gray area between PD and addiction. For example, some heavy users of marijuana suffer withdrawal when they stop using, which qualifies them as addicted. Others have no overt physical symptoms, but become psychologically disturbed.
As far as treatment is concerned, there is no real difference, apart from the possible need to detox from an addictive substance.