This from Wikipedia, but all the info is based on studies that are referenced if you want to look into it further:
A 2005 review determined that some, but not all, randomized controlled studies have found that anabolic steroid use correlates with
hypomania and increased aggressiveness, but pointed out that attempts to determine whether AAS use triggers violent behavior have failed, primarily because of high rates of non-participation.
[66] A 2008 study on a nationally representative sample of young adult males in the United States found an association between lifetime and past-year self-reported anabolic-androgenic steroid use and involvement in violent acts. Compared with individuals that did not use steroids, young adult males that used anabolic-androgenic steroids reported greater involvement in violent behaviors even after controlling for the effects of key demographic variables, previous violent behavior, and polydrug use.
[67] A 1996 review examining the
blind studies available at that time also found that these had demonstrated a link between aggression and steroid use, but pointed out that with estimates of over one million past or current steroid users in the United States at that time, an extremely small percentage of those using steroids appear to have experienced mental disturbance severe enough to result in clinical treatments or medical case reports.
[68]
A 1996
randomized controlled trial, which involved 43 men, did not find an increase in the occurrence of angry behavior during 10 weeks of administration of
testosterone enanthate at 600 mg/week, but this study screened out subjects that had previously abused steroids or had any psychiatric antecedents.
[37][69] A trial conducted in 2000 using
testosterone cypionate at 600 mg/week found that treatment significantly increased
manic scores on the
YMRS, and aggressive responses on several scales. The drug response was highly variable. However: 84% of subjects exhibited minimal psychiatric effects, 12% became mildly hypomanic, and 4% (2 subjects) became markedly hypomanic. The mechanism of these variable reactions could not be explained by demographic, psychological, laboratory, or physiological measures.
[70]
A 2006 study of two pairs of identical twins, in which one twin used anabolic steroids and the other did not, found that in both cases the steroid-using twin exhibited high levels of aggressiveness, hostility, anxiety, and paranoid ideation not found in the "control" twin.
[71] A small-scale study of 10 AAS users found that
cluster B personality disorders were confounding factors for aggression.
[72]
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