The abuse of anabolic androgenic steroids (AAS) is relatively widely spread and epidemiological studies in the western countries report a prevalence between 1-5 % among males. The impact of these steroids on the strength and muscle mass as well as many of the adverse physical effects that have been observed are well described. Several reports have also revealed severe psychological effects as results of the administration of AAS. Effects such as irritability, aggressiveness, anxiety and depression are reported to be associated with AAS abuse. The mechanistic rationales behind these effects are not well understood. Several systems are likely to be involved, including the monoamine and peptidergic systems. The aim of this review is to highlight the potential role of the neuropeptide systems in the brain with focus on how these systems are affected by repeated administration of AAS.