Alcohol and aggression: a validation study of the Taylor aggression paradigm

Analgesic Effects of Alcohol: A Systematic Review and Meta-Analysis of Controlled Experimental Studies in Healthy Participants

Despite the long-standing belief in the analgesic properties of alcohol, experimental studies have produced mixed results. This meta-analysis aimed to clarify whether alcohol produces a decrease in experimentally-induced pain and to determine the magnitude of any such effect. PubMed, PsycINFO, and Embase databases were searched from inception until April 21, 2016 for controlled studies examining the effect of quantified dosages of alcohol on pain response to noxious stimulation. Eighteen studies involving 404 participants were identified providing alcohol versus no-alcohol comparisons for 13 tests of pain threshold (n = 212) and 9 tests of pain intensity ratings (n = 192). Random effects meta-analysis of standardized mean difference (SMD) provided robust support for analgesic effects of alcohol. A mean blood alcohol content (BAC) of approximately .08% (3-4 standard drinks) produced a small elevation of pain threshold (SMD [95% CI] = .35 [.17-.54], P = .002), and a moderate to large reduction in pain intensity ratings (SMD [95% CI] = .64 [.37-.91], P < .0001), or equivalently, a mean reduction of 1.25 points on a 0- to 10-point pain rating scale. Furthermore, increasing BAC resulted in increasing analgesia, with each .02% BAC increment producing an increase of SMD = .11 for pain threshold and SMD = .20 for reduced pain intensity. Some evidence of publication bias emerged, but statistical correction methods suggested minimal impact on effect size. Taken together, findings suggest that alcohol is an effective analgesic that delivers clinically-relevant reductions in ratings of pain intensity, which could explain alcohol misuse in those with persistent pain despite its potential consequences for long-term health. Further research is needed to corroborate these findings for clinical pain states.

PERSPECTIVE

This meta-analysis provides robust evidence for the analgesic properties of alcohol, which could potentially contribute to alcohol misuse in pain patients. Strongest analgesia occurs for alcohol levels exceeding World Health Organization guidelines for low-risk drinking and suggests raising awareness of alternative, less harmful pain interventions to vulnerable patients may be beneficial.

Impact of tryptophan metabolism on the vulnerability to alcohol-related blackouts and violent impulsive behaviours

AIMS

We examined (1) the association of SLC6A4 genotypes and alcohol dependence (AD) in a sample of alcoholics; (2) the validity of lifetime occurrence of blacked-out violent impulsive behaviour (BOVIB) during binge drinking bouts as a criterion for subtyping AD patients and (3) a mechanistic hypothesis for BOVIB involving tryptophan-2,3-dioxygenase (TDO) activity.

METHODS

Three common polymorphisms of the SLC6A4 gene (5-HTTLPR, A/G SNP of LPR region and VNTR in intron 2) were genotyped. An oral tryptophan (Trp) load (OTL) was administered to a sample of patients seeking help for AD. BOVIB history and psychological status were screened by BOVIB-Q, depression (BDI), anxiety (BAI, STAI) and personality (TCI) questionnaires. During the 7 h following Trp load, serum kynurenine (Kyn) and Trp were monitored.

RESULTS

BOVIB+ patients showed significantly higher scores on depression, anxiety and character scales but no significant association was found between SLC6A4 polymorphisms and BOVIB. Patients with a history of BOVIB (BOVIB+ subgroup) differed from those exempt from such episodes (BOVIB- subgroup) for TDO activity response to OTL assessed by the Kyn:Trp ratio (P = 0.043) and the slope of concentration increase ratio (SCIR) of serum Kyn (P = 0.043).

CONCLUSIONS

Put together, these findings support the validity of the BOVIB criterion to differentiate a sub-group of vulnerable AD subjects and suggest that OTL may help to concurrently define a specific endophenotype.

Drugs of abuse and the elicitation of human aggressive behavior

The drug-violence relationship exists for several reasons, some direct (drugs pharmacologically inducing violence) and some indirect (violence occurring in order to attain drugs). Moreover, the nature of that relationship is often complex, with intoxication, neurotoxic, and withdrawal effects often being confused and/or confounded. This paper reviews the existing literature regarding the extent to which various drugs of abuse may be directly associated with heightened interpersonal violence. Alcohol is clearly the drug with the most evidence to support a direct intoxication-violence relationship. The literatures concerning benzodiazepines, opiates, psychostimulants, and phencyclidine (PCP) are idiosyncratic but suggest that personality factors may be as (or more) important than pharmacological ones. Cannabis reduces likelihood of violence during intoxication, but mounting evidence associates withdrawal with aggressivity. The literature on the relationship between steroids and aggression is largely confounded, and between 3,4-methylenedioxymethamphetamine (MDMA) and aggression insufficient to draw any reasonable conclusions. Conclusions and policy implications are briefly discussed.

Effects of alcohol on cardiovascular reactivity and the mediation of aggressive behaviour in adult men and women

AIMS

Recent models have proposed several pharmacological means by which alcohol may produce heightened aggression, among them that alcohol may both hyper-arouse the reward system and diminish the threat detection system. The current study examined these hypotheses employing heart rate and blood pressure as physiological indices of arousal, examining whether arousal differed by alcohol group, and if this related to level of aggression.

METHODS

Participants were 32 males and 32 females, aged 18-30 years, screened for physical and psychological disorder, who competed on the Taylor aggression paradigm. The gender groups were further split into half sober, half intoxicated. Arousal was measured at baseline, post-beverage consumption, and post-aggression paradigm.

RESULTS

Participants in the alcohol condition initially demonstrated slight heart rate elevations and blood pressure decreases, but showed little arousal in response to the aggression paradigm, whereas sober participants demonstrated considerable arousal on both indices. Intoxicated participants were more aggressive than sober controls; men and women did not differ significantly. Regression analyses demonstrated that change in systolic blood pressure from post-beverage consumption to post-aggression paradigm acts as a mediating variable in the alcohol-aggression relationship.

CONCLUSIONS

These results lend support to the stress-response dampening model of the alcohol-aggression relationship, and moreover suggest that the magnitude of intoxicated aggression is related to the magnitude of that dampening.

Aggressive and nonaggressive behavior as a function of alcohol intoxication and frustration in women

An experiment tested whether alcohol increases aggression in women in a situation in which both an aggressive and a nonaggressive response alternative of equal instrumentality and of equal variability are available. Subjects were assigned to one of three groups, namely, an alcohol, a placebo, or a control group. The alcohol dose was 1.0 ml of pure alcohol/kg body weight. After drinking their respective drink, subjects were instructed to supervise a bogus partner on a visual scan test over a series of trials. Each time this partner made a mistake, subjects could either give an uncomfortable electric shock (scale 1 to 10) or a comfortable vibration (scale 1 to 10) to the partner. Aggressive and nonaggressive behavior was measured as numbers, intensities, and durations of shocks or vibrations, respectively. Neither alcohol nor frustration differentiated the groups on aggressive or nonaggressive behavior. All groups were significantly more inclined to use the nonaggressive alternative irrespective of alcohol dose and level of frustration. In conclusion it was stated that women do not increase their aggression as a function of alcohol in a situation with more than one response alternative available. The need to incorporate gender differences as to aggressive effects of alcohol was stressed.

Ethanol effects in an anxiety/defense test battery

Two tests, components of an Anxiety/Defense Test Battery, have been designed to measure risk assessment, inhibition of nondefensive behaviors, and movement arrest, all of which occur in the natural defense patterns of rats to threatening stimuli. In these tests, which used a nonpainful threat stimulus (a cat), ethanol (0.6 and 1.2 g/kg) increased two risk assessment behaviors on an initial test day, and produced a wider pattern of changes in all three patterns on a retest (no cat) day, 5 days later. The pattern of results obtained is compatible with a view that defensive behaviors occur in a fixed sequence with the decreasing intensity of threat an important factor in the transition from one defensive behavior to the next, and with ethanol at these doses producing a mild and relatively nonspecific anxiolytic effect. Comparison of male and female subjects on these tasks also suggested that females are more defensive than males, a finding which agrees with a variety of human anxiety studies but is at variance with previous rodent literature.

Alcohol and the validation of experimental aggression paradigms: the Taylor reaction time procedure

The aim was to find out whether intoxicated and sober subjects would calibrate a shock scale to the same objective level and whether shocks received would be subjectively experienced in the same way in terms of pain and discomfort. The intention was also to replicate previous studies attributing an aggression enhancing effect to alcohol. The subjective ratings were made within the Taylor reaction time 'aggression machine'. Twenty-four subjects were randomly assigned to either an alcohol or a control group. The former drank 0.8 ml of pure alcohol/kg body wt. Results indicated no differences among groups on a shock setting measure of aggression under unprovoked or provoked conditions and no differences in level of calibration of shocks or in subjective ratings of pain and discomfort. These results were contrary to all predictions and are discussed as indirectly supportive of an hypothesis stating that this version of the 'aggression machine' may not generate a valid measure of aggression when used in alcohol research.

Beer intoxication and physical aggression in males

Twenty subjects participated in an experiment testing the effects of a moderate dose of beer on physical aggression. Subjects were randomly assigned to a beer drinking group or a control group. Aggression was measured in terms of number of shocks given, shock intensity, and shock duration in a modified version of the Buss' aggression machine. There were no differences among groups and there was no interaction of beer by frustration on aggression. The results are explained in terms of expectancies held by subjects as to the effects of beer intoxication on behaviour.

Alcohol and unpleasant stimulation: subjective shock calibration and pain and discomfort perception

In an experiment 8 men participated in an alcohol and a sober condition in a rotated order. In both conditions subjects first calibrated a shock scale to a subjective criterion and then rated their subjective pain and total discomfort. Subjects calibrated the shock scale higher when intoxicated and rated the calibrated level equally painful in the sober and intoxicated conditions, but when intoxicated subjects actually rated the higher shock level as less uncomfortable. The shock scale was calibrated higher under intoxication not because subjects wanted to impress the experimenter but because less pain and discomfort was actually experienced.

Alcohol, frustration, and aggression: an experiment using the balanced placebo design

In a balanced placebo experiment it was hypothesized that pharmacological effects of alcohol would override expectancy effects and that alcohol would increase aggression only under frustrative conditions by a process of an exaggerated subjective experience of frustration. In a modified “aggression-machine” frustration was defined as arbitrary and manipulated in a within-subjects fashion. Manipulation checks indicated difficulties in deceiving subjects as to the content of the drink, and it was not possible to evaluate pure pharmacological effects. Ratings of subjective frustration did not differentiate experimental groups. Only during frustrative conditions did intoxicated subjects increase their aggression regardless of information about drink's content. Frustration per se and expectancy factors did not lead to increased aggression. This was explained in terms of a more narrow focusing on outstanding available response alternatives and as opposed to the 1983 Taylor and Leonard explanation of alcohol-increased aggression.

Alcohol, aggression and the validity of experimental paradigms with women

A study tested if women are influenced in the Taylor aggression paradigm by different information about the state of intoxication in their faking men partners. Earlier results for men indicated the operation of a confounding variable in this respect. Women like men expected intoxicated partners to be more aggressive but unlike men did not choose a more aggressive mode of responding. Different explanations were suggested, for instance in terms of women's attitudes to electric shocks, different perceptions of provoking stimuli, and attributions. With women this paradigm is valid but may be insensitive to experimental manipulations.