I keep going back to this post at Dr. Joyner's. An excerpt from the link:

The stimulation of the emotional centres shows that shopping is a stress relief. People do not have to think, and the brain rewards them with pleasurable feelings. By shopping, they are bypassing stress and just going with the pleasurable flow,'' he added.

Isn't even the most mundane shopping a form of stress relief? Who isn't greatly relieved when they replenish their toilet tissue supply? Or coffee? Or bath soap? Or milk?