Some drugs, particularly when used to excess and/or used illegally, significantly increase the risk for aggressive behavior and the commission of acts of violence. Alcohol, anabolic steroids, benzodiazepines, and cocaine are key drugs that can escalate the development of aggression and violent behavior.
Alcohol is a legal drug for individuals ages 21 and older, but when used to excess, it can cause aggressive and violent behavior against family members and others. According to Mark S. Gold, M.D., in his 2010 book, "The Encyclopedia of Alcohol Abuse and Alcoholism," aggression may occur with alcohol abuse because the balance of brain chemicals such as serotonin is disrupted, enabling impulsive and aggressive behaviors to gain dominance. Gold also says that alcohol may trigger violence in individuals who are otherwise predisposed to violence.
In a 2005 study of intimate partner violence by Christopher M. Murphy and colleagues, 40 male alcoholics and their partners were interviewed about acts of physical aggression toward others. The researchers found that the amount of alcohol consumed---with heavy consumption more likely to lead to aggression---was significant in 72 percent of the cases of men who admitted they had engaged in violence. The researchers also found that acts of physical aggression that were linked to alcohol abuse were most likely to occur between 5:00 p.m. and midnight.
According to the National Institute of Drug Abuse, or NIDA, the psychiatric effects of steroid abuse include rage and aggression as well as mania and delusional behavior. Anabolic steroids are drugs that are used illegally, usually to build up muscle mass more quickly than exercise alone can achieve. NIDA reports that some users of steroids get into physical fights with others or commit aggressive crimes such as armed robbery, behavior that is not typical for the individual when not taking steroids.
Benzodiazepines---anxiety-reducing drugs---may elicit aggressive behavior in some users. In a study of 30 males, including 15 taking diazepam, also known as Valium, and 15 on placebo, researchers Patricia S. Wallace and Stuart P. Taylor had the subjects choose what they believed to be were shock settings for their opponents in a task. The subjects taking diazepam chose significantly higher shock settings than the placebo subjects, indicating greater levels of aggression than the subjects in the placebo group. The reason for higher aggression levels with diazepam is unknown.
Cocaine, a stimulant and a drug of abuse and dependence, can increase levels of violence and aggression among users. In a study of 489 subjects undergoing treatment for aggression prevention, including 76 percent males and 24 percent females, Regan L. Murray, Ph.D., and colleagues noted in their 2008 article that aggression was linked to the use of cocaine, as well as with the heavy abuse of alcohol. The researchers found 60 percent of the subjects reported having committed acts of physical aggression and 47 percent said they had injured a non-partner.
A new substance, cocaethylene, is formed when an individual abuses both cocaine and alcohol, according to Gold. This substance is more toxic than either alcohol or cocaine alone. It is unknown whether cocaethylene may escalate aggression.