Alcohol consumption is often linked to the manifestation of increased aggression in a person. Every third crime is committed in a state of alcohol intoxication, and in the case of violent crimes, such as domestic violence and murder, this figure can even reach 80%. It would seem that the link between alcohol and violence is quite direct. However, in this matter, as in many others, one should not make the survivor’s bias mistake—considering only the clearly observable results while ignoring those that we had no opportunity to observe. Not all people become more aggressive from alcohol. Of course, some of them may become angry under its influence, and we notice this well. But at the same time, others will begin to feel sad or exhibit some other emotions. And a very important role in what behavior can be expected from alcohol consumption is played by the person’s neurophysiology.
As studies on primates have revealed, differences in the functioning of the serotonin system and the negative influence of the environment are important factors in alcohol-induced aggression. In rhesus macaques, stressful circumstances, such as separation from parents and social isolation at an early age, led to the suppression of the serotonin system’s work, increased aggressiveness, and excessive alcohol consumption when it was freely available. However, it is very important to specify that the negative influence did not have such an effect on all monkeys—only carriers of the short allele of the serotonin transporter gene were susceptible to it. At the same time, carriers of the long allele were more resilient and did not experience the negative consequences of such influence. It can be concluded that a genetic predisposition to greater sensitivity to stressful circumstances, which causes disruptions in the functioning of the serotonin system, leads to increased alcohol consumption and aggression.
Increased alcohol consumption was observed also in mutant mice lacking the serotonin 1B receptor gene, while stimulation of the serotonin 1A receptor can lead to a decrease in its consumption. Additionally, studies on mice confirmed that not all individuals become aggressive from alcohol consumption. Increased aggression was observed only in individuals who had significantly reduced (by 49-76%) levels of mRNA of all serotonin receptors (except 3A) in the prefrontal cortex of the brain and some other abnormalities in serotonin function.
It is also worth highlighting that empathy is an important mediating factor in this matter. Thus, men (but not women) with low levels of empathy exhibit increased aggression from alcohol consumption. Furthermore, in two samples (a clinical sample consisting of 703 psychiatric institution patients, and a community sample consisting of 870 students), it was shown that the level of psychopathic traits mediates the influence of alcohol dependence on the commission of violence against romantic partners. At the same time, alcohol dependence on its own, separate from psychopathic traits, showed an insufficient link with violence to be considered a predicting factor. As noted, research on violence against romantic partners should take into account the potential role of psychopathy, especially if the influence of alcohol consumption is being studied.
Of course, consuming large quantities of alcohol entails many negative consequences for a person. However, in the case where a person exhibits violent behavior under alcohol intoxication, we cannot place all the blame solely on alcohol. It is merely another provoking factor, not the cause of the violence, for which the therapeutic solution must be sought. The root of the problem of violent behavior and the increase in the level of psychopathic traits in an individual lies in the disruption of the violence inhibition mechanism, the functioning of which is handled by the serotonin system. In the case of violence, it is the dysfunction of this mechanism that primarily requires therapy.

