Shopping addiction is caused by, primarily, the fact that you can get a physiological perk from buying something which initially you want.

Even down the road, people with shopping addictions find they feel a need to get that little perk, or burst of positive feelings.

So shopping addiction, like other behavioral addictions and non-behavioral addictions such as alcohol or drugs, provides a biochemical change in the individual which elates them, that is desired, invites pleasure or removal of pain or despair, and it works.

It's predictable. You specify the object you want, you give them the credit card, you obtain it, and there is this flush of energy. Actually brain activity occurs when you purchase something at the store or again on line. It is rewarding.