pyschological addictions DO have a chemical component... your own brain's production of hormones and other neuro-chemicals.
For example: exposure to pornography and other sexually addictive activities cause severe spikes in dopamine and a few other neuro-chemicals, which deal with, among other things, the brain's reward mechanic for social interactions. The feeling of friendship and the feelings of closeness to the one that is loved are all sub-functions of this. Repeated exposure to the extreme spikes causes the brain to reset its homeostasis for those chemicals to a higher level, or in other words, develop perceived need for constant elevated levels thereof, and a resistance to said neuro-chemicals, which increases the more often exposure takes place. As a result, normal social interactions, and even the normally more powerful interactions between lovers, no longer feel rewarding - there is a sensation of disconnect that grows and increases the more exposure to the spikes occur. This in turn generally results in the afflicted individual seeking out different and stronger sources of stimulus, as well as feeling isolated from those with whom they previously associated and those around them in general. It also tends to cause those who don't provide direct or indirect stimulus to be perceived as unimportant, meaningless, and inconsequential to the one so afflicted. One's own brain manufactures the drug of choice, all one has to do is find something increasingly stimulating to look at, touch, or do.
(this is a minimal, cut-down example - lots of details have been left out.)