Anabolic androgenic steroids (AAS), a synthetic version of the male sex hormone testosterone, are sometimes used as a medical treatment for hormone imbalance. But the vast majority of AAS is used to enhance athletic performance or build muscle because when paired with strength training. AAS use increases muscle mass and strength, and its use is known to have many side effects, ranging from acne to heart problems to increased aggression. A new study now suggests that AAS can also have deleterious effects on the brain, causing it to age prematurely.