Alcohol and aggression
Anger and ethanol may be even more closely tied than we thought
by Barry Gilbert, MD
Vol.19, No.06, August 2011

Paul and Grace became aware in their marital therapy that they had a pattern of getting into arguments in the evenings after they’d had 1 or 2 glasses of wine “to relax.” They both noted that Grace tended to become easily angered in the evenings. Their therapist suggested that their moderate use of alcohol was making the resolution of the problems they were encountering even more difficult.

The relationship between alcohol and aggression is well known, especially at the extreme ends of behaviour. Studies have found that up to 86% of people committing homicide and 60% committing sexual assault had consumed alcohol at the time of the offense. The relationship between alcohol abuse or dependence and violence in those with antisocial personalities (those with a pervasive pattern of disregard for and violation of the rights of others) is also well known. Is there an increase in aggression at more moderate levels of alcohol consumption?

Alcohol weakens brain mechanisms that usually restrain impulsive behaviour, suggest several researchers. Anna Freud once famously described the superego, that psychoanalytic term for the conscience that guides behaviour, as: “that part of the mental apparatus that is soluble in alcohol.” Recent work has found that alcohol impairs information processing, direction of attention and working memory. This leads the drinker to misinterpret social cues, to miss cues that might de-escalate a situation; to perseverate on one view of a situation, usually with a more paranoid hue. Lack of working memory impairs the ability to reflect and to generate alternate views of what’s happening and alternate options for reaction.

A stressful game

A new study, provocatively entitled “Alcohol Dose and Aggression: Another Reason Why Drinking More is a Bad Idea” (Duke MM, et al. J Stud Alcohol Drugs 2011;72:34-43) now provides new insight into this question. Researchers gathered a large sample of 95 men and 92 women, all healthy social drinkers with no substance or psychiatric problems. Participants were randomized to 5 groups receiving doses ranging from 0.125 mg/kg of alcohol (a placebo dose) to a heavy dose of 1.0 mg/kg — equal to about 5 drinks for a 70 kg person. All subjects were blind to the dose they received. There was also a control group that received no alcohol. Aggression was measured using a game format. Participants played a somewhat stressful game against a hidden “opponent” (actually a computer) that required quick responses. When they lost a round, subjects received a one second shock of varying intensity. Every time they won a round, they were allowed to select the intensity and duration of the shock given to their opponent. All were told that the opponent was also drinking. Aggression was measured by the type of shocks participants delivered to their “opponents.”

Quantity matters

The investigators discovered that there was a linear increase in aggression with increasing alcohol dose. They found a significant increase in aggression beginning at a dose of 0.75 mg/kg (about 3-4 drinks for a 70 kg person). The linear increase in aggression with increasing alcohol dose applied to both men and women in the study. The researchers felt that their data best fit a linear model and concluded that there was no clear threshold beyond which alcohol began to elicit aggression. Instead, they found that lower doses of alcohol had a “meaningful” effect on aggression. Each increment of alcohol dose in the study was accompanied by an increase in the level of aggression. They interpreted their results to contradict previous suggestions that lower doses of alcohol might decrease aggression by producing “a state of affective tranquillity.”

Aggression is a complex behaviour with many determinants in the biology and psychology of a person. Environmental and cultural factors are also important in many cases. This research is notable for the large number of subjects and the fine-grain detail of the doses of alcohol. It suggests clinicians should maintain a lower threshold for considering alcohol use as a complicating factor in problems involving aggression.

Barry L. Gilbert, MD, CCFP, FRCPC is a psychiatrist, psychoanalyst and Assistant Professor of Psychiatry at the University of Toronto.
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