People underestimate the neurochemical activity of AAS. They indirectly increase dopamine signaling by binding to neuronal androgen receptors in key reward-related brain regions.
This facilitates dopamine bursts tied to specific behaviors (like working out and strutting around in a string top, arms spread wide in a shameless display of ILS)
In other words, motivation becomes context-dependent. Dopamine neurons over-respond to particular triggers. As a result, the gym rat become more addicted to his gym rat lifestyle and Big Man identity, not to PEDs themselves (unlike stimulant drugs like coke or amohetamines, which produce massive baseline dopamine spikes)
Inevitably, the brain compensates by lowering baseline dopamine.
Responsiveness to natural rewards collapses when the drug is removed. Paired with joys of going hypogonadal, it's easy to see how addiction begins to lurk in the backround..