As noted by New York Daily News, Sally McNeil’s history of violence undermined her defense’s argument because it made it difficult to prove that her decision to murder her husband was caused by her steroid usage. And in many ways, this reflects the murky nature of the research on this subject.

Despite studies linking anabolic steroids to aggression and irritability, other research reveals the possibility that additional variables are part of the equation. In particular, certain personality traits that are more commonly found in steroid users could play a significant role. The National Institute on Drug Abuse pointed to research that suggested personality traits linked to mental health issues such as borderline, antisocial, and histrionic personality disorders could be more frequently found in people who use steroids, which would muddy the significance of the link between steroid use and aggression.

Still, WedMD noted that Jill M. Grimes, a behavioral psychologist with Northeastern University in Boston, conducted a study on preadolescent hamsters that found a link between steroid use and alterations in brain regions that are involved in aggression. While individuals like Sally McNeil appear to already have dysfunctional aggression, Grimes’ research suggests that steroid use in young hamsters — and possibly humans — can increase aggression.