Cannabis and aggression in animals

Endocannabinoid system and aggression across animal species

This narrative review article summarizes the current state of knowledge regarding the relationship between the endocannabinoid system (ECS) and aggression across multiple vertebrate species. Experimental evidence indicates that acute administration of phytocannabinoids, synthetic cannabinoids, and the pharmacological enhancement of endocannabinoid signaling decreases aggressive behavior in several animal models. However, research on the chronic effects of cannabinoids on animal aggression has yielded inconsistent findings, indicating a need for further investigation. Cannabinoid receptors, particularly cannabinoid receptor type 1, appear to be an important part of the endogenous mechanism involved in the dampening of aggressive behavior. Overall, this review underscores the importance of the ECS in regulating aggressive behavior and provides a foundation for future research in this area.

The Relevance of Sex in the Association of Synthetic Cannabinoid Use With Psychosis and Agitation in an Inpatient Population

BACKGROUND

Current evidence suggests that women are more sensitive to the effects of cannabinoids. The aim of this study was to investigate the relevance of sex in the association of synthetic cannabinoid (SC) use with psychosis and agitation.

METHODS

A retrospective chart review was conducted for patients admitted to a psychiatric unit (2014-2016) to extract information on demographic factors, use of substances, clinical symptoms, and pharmacologic treatments. Study groups were defined as SC users (anyone who reported use of SCs over the past 3 months), cannabis users (positive toxicology screen for Δ⁹-tetrahydrocannabinol [THC]), and controls (those who denied use of SCs over the past 3 months and had negative toxicology for THC).

RESULTS

Digital charts of 983 patients were reviewed. A total of 162 subjects reported use of SCs over the past 3 months (76% male), and 292 subjects had positive toxicology screen for THC (67% male). A total of 38.9% of SC users (n = 63) had positive urine toxicology screen for THC. SC users had higher risks of psychotic presentations (adjusted odds ratio [AOR] = 3.390; 95% CI, 1.390-8.267) and agitation (AOR = 4.643; 95% CI, 1.974-10.918) compared to the controls. While women had lower rates of psychosis than men in the cannabis and control groups, the rates were markedly potentiated with SC use to high levels (79%) approximately equal to that seen in men (80%). There was also a significant interaction between SC use and sex for agitation (AOR = 0.308; 95% CI, 0.117-0.808). Female SC users were significantly more agitated than male SC users (73.7% vs 47.6%, respectively, P = .005).

CONCLUSIONS

SC users are more likely than nonusers to be psychotic or agitated in an inpatient setting. The potentiated rates of psychosis and agitation with SC use in women suggest that they may have a greater sensitivity to these synthetic compounds.​.

Delta9-tetrahydrocannabinol stimulates palatable food intake in Lewis rats: effects of peripheral and central administration

To further study effects of delta9-tetrahydrocannabinol (THC) on food intake, male Lewis rats were maintained on rat chow and, on testing days, presented with chocolate cake batter (CCB) for 4h in addition to chow. Chow intake was not affected by THC administration in either experiment. In experiment 1 (n = 13) THC was administered intraperitoneally, and low doses produced increases in CCB intake for up to 1 h while the highest dose significantly decreased CCB intake over this same time period. In experiment 2 (n = 10) THC was injected intracerebroventricularly. Doses of 2.5, 10 and 25 microg significantly increased CCB intake for up to 1 h while stimulatory effects following 5 microg lasted up to 2h. Overall THC produced short-term increases in palatable food intake following both peripheral and central administration. Intraperitoneal administration resulted in an "inverted U" dose-response curve at all time points, while all central doses resulted in increased intake early in the time course and the hyperphagic effects were of greater duration than those following peripheral administration.

Cannabis and delta-9-tetrahydrocannabinol. Effects on elements of social behaviour in mice

Behavioural effects of cannabis and delta-9-tetrahydrocannabinol (THC) in male mice encountering solvent-treated males, and of cannabis in males encountering control females, were examined by ethological procedures. Effects on elements and element-groups within behavioural categories were investigated, and effects of cannabis on the response sequence to the behaviour of male partners examined. Effects were detected on elements that previously had been grouped within categories. Flight elements "flag, evade, retreat and flee" and immobility were increased both by cannabis (50 and 100 mg/kg in male-male encounters and 25 mg/kg in male-female encounters) and by THC (5 mg/kg), whereas "scan", "wash and self-groom" and some elements of social investigation were reduced. Bout length and duration of "explore" were increased by THC. In encounters with females, cannabis decreased sexual behaviour. Sequence analysis showed that cannabis, within the limitations of the comparatively small size of sample, to have no significant effect upon normal behavioural responses at 50 and 100 mg/kg, apart from enhancement of the flight response to aggression and some elements of social investigation by partners. These more detailed analyses revealed effects that would not be detectable by the conventional approach.

Aggression in adolescents. Aspects of pathogenesis

The violent adolescent presents considerable difficulty to society and to health care professionals. Thus, this discussion overviews some theories of pathogenesis regarding aggression in adolescence. There is special emphasis on related concepts of neuroanatomy and neurobiochemistry, as well as hormonal influences and the associated psychosocial environment. Literature about the importance of drug abuse and the media is also reviewed. In addition, studies relating aggression to epilepsy and electroencephalographic changes are considered. It is hoped that this paper will aid the interested clinician discern the vast and multidisciplinary literature describing aggression in adolescence. Future investigative endeavors will provide, it is hoped, more definitive biologic and social measurements to enable specific prevention and intervention strategies.

Chronic delta 9-tetrahydrocannabinol administration and schedule-induced aggression

The effects of 0.5 mg/kg and 1.0 mg/kg of delta 9-tetrahydrocannabinol (delta 9-THC) on key-pecking maintained by a response-initiated fixed interval (FI) schedule of food presentation and schedule-induced aggression in the pigeon were studied. Initially, following the administration of delta 9-THC both the rate of key-pecking and attack responding were markedly reduced. Over sessions, tolerance developed to the suppressant effect on key-pecking, with the rate returning to the predrug level. The suppressing effect of delta 9-THC on the rate of attack remained at or near zero throughout the series of delta 9-THC injections.

Comparison of the effects of alcohol, chlordiazepoxide, and delta9-tetrahydrocannabinol on intraspecies aggression in rats

The species-specific repertoire of attack, threat, defense, and submission was produced in pairs of male laboratory rats and measured after intraperitoneal injection of a drug or its vehicle to one of the rats. Attack behavior by dominant rats toward nondrugged opponents was increased by a low dose of alcohol (0.5 g/kg) or of chlordiazepoxide (5 mg/kg), but suppressed by delta9-tetrahydrocannabinol (THC). In experienced subordinate rats, the highest alcohol dose (1.5 g/kg) impaired the defensive upright posture whereas THC (2, 4 MG/KG) prolonged immobile crouch and submissivesupine reactions and resulted in more wounds. Naive rats administered alcohol assumed the submissivesupine posture more readily and for a longer duration, but sustained more biting attacks. Chlordiazepoxide and THC, when administered to naive rats, prolonged the immobile crouch reaction, and THC also impaired the defensive upright posture. We conclude that alcohol and chlordiazepoxide both enhance attack behavior in dominant rats, whereas THC has specific anti-aggressive effects and profoundly alters the submissive-defensive reactions.