Anabolic/androgenic steroid use may be associated with insomnia. This adverse reaction appears to be related to an imbalance of hormone levels, and has been noticed during both excess and insufficient hormonal states. For example, insomnia is a common complaint among men suffering from low androgen levels (hypogonadism). It is also frequently reported by steroid abusers during the post-cycle refractory period, when endogenous androgen levels are also low due to steroid-induced suppression. At the same time, this side effect is also seen during active AAS administration, when androgen levels are very high.
The full etiology of steroid-related insomnia is not fully understood, although increased cortisol or diminished estrogen is commonly blamed. Given the complex interactions between sex steroids and the human psyche, it is difficult to predict how and when this adverse reaction will appear. While insomnia may be frequently reported among steroid users, this side effect rarely reaches a clinically significant level.
Wlliam Llewellyn (2011) - Anabolics