Amphetamines and Their Effects on Human Aggressive Behavior


Because the possession, use, and distribution of amphetamine are illegal and because the compound causes brain damage, ethical concerns have prevented experimental research on the behavioral effects of amphetamine. Thus, the available literature on the effects of amphetamine in human participants is all correlational. Although there have been reports of high correlations between violent crime and amphetamine use, these studies may be confounded because other drugs such as alcohol are often involved and users that commit these acts sometimes have aggressive tendencies beforehand (). The existing literature does give some indication regarding the effects of various doses and the possible predictions one can make concerning the long-term effects on mental health, but until more research can be performed we are limited in our understanding the relationship of amphetamine with human aggressive behavior.

Subjective Analysis

The advantage of experiments involving human subjects is that people have the ability to describe their immediate emotional states and report their feelings and thoughts. However, these subjective analyses can sometimes be inaccurate, and in a sense become “contaminated” because of participants’ biases or reservations concerning the personal information they disclose, especially if it involves substance abuse. In a self-report study involving amphetamine users from a metropolitan city in Australia, Vincent et al. (1998) reported that more than one third of the sample comprising 100 participants had experienced symptoms of depression and anxiety prior to their amphetamine use, and nearly one third had experienced previous mood swings and aggressive outbursts. In addition, some of the participants believed that their usage had intensified these conditions, and almost a quarter of the subjects felt symptoms of depression and anxiety attacks for the first time after they started using the drug, although not all of them associated these symptoms with their amphetamine use. Other research shows decreases in fatigue, increases in vigor, no significant changes in anger or confusion, and a moderate decrease in depression (). Different subjects from separate studies also show signs of excessive confidence and delusional paranoia ().

In subjective experiments, it is important that the participants understand completely what it is that they are analyzing in order to obtain accurate results. When studying the effects of amphetamine on human aggressive behavior, it is essential that we distinguish this aggression from negligent, violent crime. Although there is no clear-cut line that separates the two, we can think of violent crime as forceful and offensive acts that violate the norm and possibly lead to malevolent physical violence, whereas aggression is a “hostile or destructive tendency or behavior” (). One could therefore generalize from this distinction that violence has a more social, and perhaps even economic, connotation, whereas aggression appears to be associated more closely with psychological factors. In Wright and Klee’s (2001) study the respondents were asked about any ongoing problems they may have been experiencing with amphetamine-related aggression, and were “encouraged to include in their response incidents that did not result in physical harm to others, but which had produced a conscious awareness of their own hostility.” By making such a distinction, one can acquire accurate data that are more representative of the population.

Observed Behavior

Experiments have been carried out that use positive and negative reinforcement to examine the effects of amphetamine on aggressive behavior. In one such study, subjects were given the opportunity to gain points that were redeemable for a monetary reward by pressing an assigned button. This was the non-aggressive response. Their point values were systematically reduced by a fictitious partner from whom they could subtract points by pressing a different button, which was the aggressive response. Biphasic results similar to those reported in nonhuman research were observed, with lower doses (5 and 10 mg/70 kg) of d-amphetamine increasing the rate of aggressive responses and higher doses (20 mg/70 kg) reducing these occurrences to levels found after placebo administration (). Another noteworthy outcome was that while the rate of aggressive responses was decreased at the highest dose, the amount of non-aggressive responses remained unaltered.

Referring back to the Vincent et al. (1998) study, one can extrapolate generalized correlations between amphetamine use and the behavior and health of the user. One of the outcomes of this analysis was that symptoms such as depression and anxiety were likely to be intensified, and additional problems including paranoia and aggression could possibly arise with continued use. Furthermore, it was determined that a direct relationship existed between increasing severity of dependence and mental and physical health deficits, which was consistent with the fact that the sample used in the study had considerably poorer mental and physical health and emotional functioning when compared to the general South Australian population. These data support the popular opinion that amphetamines can have severe and detrimental effects on both physical and mental performance.