Cannabis And Aggression


Cannabis is widely regarded as a “peace” inducing drug, a legacy of the hippie era in the 1960s. Relaxation and stress relief are among the most commonly reported reasons for use of the drug, and IDMU surveys have found “reduced aggression” to be a commonly-perceived “benefit” of using the drug. Several synthetic cannabinoids have been investigated as sedative/relaxants. Studies of cannabis and driving have identified a reduction in aggressive driving or risky manoevres as an explanation for the relatively low level of impairment, or even beneficial effects, on driving performance. However, firm evidence of reduced aggression in humans is limited.

In a study of urine toxicology following psychiatric emergency admissions, Dhossche reported “Various indices of substance abuse, including… cannabis, were not associated with aggressive behavior.” In a study of offenders referred to a South African psychiatric unit, Hemphill et al concluded “(cannabis) appeared to diminish the action of alcohol, and may inhibit urges toward violence and rape in aggressive persons and psychopaths.” In Egypt, Souief reported “Compared with controls, cannabis takers were… low on quarrelsomeness and high on selflessness”

In mice, cannabinoids appear to reduce “attack” behaviour, increase submissive behaviour, the “flight” response to aggression. “Intruder males” treated with hashish “were more frequently attacked and submission and flight was increased”. Ham et al found “THC produced a dose dependent depression of aggression in isolated mice” while Cutler et al also found a rebound effect, with dominant males showing an increase in aggression one week following withdrawal of cannabis. In rats, THC (but not CBD) was found to reduce aggressive responses and increase avoidance behaviour in male-male encounters, as well as to reduce predatory aggression.

In baboons, Sieber reported “In the “approaching” male the drug reduced “approach” and the aggressive elements “hit-ground”, “brows-back” and “attack” but increased the frequency of “retreat”. Social interactions were generally diminished. In the “retreating” male friendly social interactions as “lipsmack” and “touch-back/handle-genitals” were suppressed but the threatening elements “open-mouth” and “tooth-grind” were stimulated. “Retreat” was additionally more frequent.”, However Lewett et al reported that baboon responses varied considerably between individual animals, and Sassenrath et al, working with monkeys, found a biphasic reponse with increased aggressive responses following development of tolerance to the drug effects.

However some researchers have reported increased “aggressive” responses on human or animal behavioural models, Carlini et al reported increased aggressive behaviour in THC-dosed rats following deprivation of REM sleep, or after developing tolerance to morphine. Dorr et al reported that a high THC dose (2.5 mg/kg) “markedly increased the percentage of animals which showed both aggression and flight acts–a rare combination among controls.” Clinicians have reported a toxic psychosis following prolonged or heavy cannabis use, including aggressive behaviour or panic disorder, however the existence of a specific “cannabis psychosis” is not firmly established in the absence of an underlying psychopathology.

Drugs used to treat aggression and violence have included antipsychotic drugs (major tranquilliers such as chlorpromazine), minor tranquillisers (benzodiazepines), lithium, anticonvulsants, and hormonal therapies. All of the above therapies involve risks, including extrapyramidal symptoms (uncontrolled movements) from phenothiazines, and severe dependence from benzodiazepines.

While the effects of cannabis on aggression in humans have not been adequately studied, there is evidence from animal studies that cannabis (THC) can reduce aggressive behaviour in response to challenge, rendering the subject more likely to avoid an aggressive incident or aggressive responses to a threat. However, for some individuals heavy use of cannabis may precipitate a psychotic reaction with aggressive outbursts. These incidents are relatively rare, and highlight the varied individual responses to the drug. The preponderance of scientific evidence does suggest cannabis may have a role in reducing aggressive behaviour, and the drug is certainly perceived to do so by a large number of cannabis users.


Stanton MD (1976) Drugs, Vietnam, and the Vietnam veteran: an overview. Am J Drug Alcohol Abuse 3(4):557-70

Morningstar PJ (1985) Thandai and chilam: traditional Hindu beliefs about the proper uses of Cannabis. J Psychoactive Drugs 17(3):141-65

Allen JR, West LJ (1968) Flight from violence: hippies and the green rebellion. Am J Psychiatry 125(3):120-6

IDMU (1998) submission to House of Lords Enquiry – Cannabis, the Scientific & Medical Evidence. Volume of Evidence – House of Lords HL 151-I London: The Stationery Office

Reilly D, Didcott P, Swift W, Hall W (1998) Long-term cannabis use: characteristics of users in an Australian rural area. Addiction 93(6):837-46

Dixon L, Haas G, Weiden PJ, Sweeney J, Frances AJ (1991) Drug abuse in schizophrenic patients: clinical correlates and reasons for use. Am J Psychiatry 148(2):224-30

Dube KC, Kumar A, Kumar N, Gupta SP (1977) Drug use among college students–an interim report. Bull Narc 29(1):47-61

IDMU (1998), Atha MJ & Blanchard S (1997) op cit.

Mechoulam R, Carlini EA (1978) Toward drugs derived from cannabis. Naturwissenschaften 65(4):174-9

Ward NJ & Dye L (1999) Cannabis and Driving – a review of the literature and commentary. DETR Road Safety Research Report No 12. London: DETR

Bailey J (2000), quoted in the Press (New Zealand), 22-4-2000

IDMU (2000) Regular Users III – Cannabis and Driving – in prep.

Dhossche DM (1999) Aggression and recent substance abuse: absence of association in psychiatric emergency room patients. Compr Psychiatry 40(5):343-6

Hemphill RE, Fisher W (1980) Drugs, alcohol and violence in 604 male offenders referred for inpatient psychiatric assessment. S Afr Med J 57(7):243-7

Soueif MI (1975) Chronic cannabis takers: some temperamental characteristics. Drug Alcohol Depend 1(2):125-54

Kilbey MM, Fritchie GE, McLendon DM, Johnson KM (1972) Attack behaviour in mice inhibited by -9-tetrahydrocannabinol. Nature 238(5365):463-5

Frischknecht HR, Siegfried B, Schiller M, Waser PG (1985) Hashish extract impairs retention of defeat-induced submissive behavior in mice. Psychopharmacology (Berl) 86(3):270-3

Cutler MG, Mackintosh JH (1975) Effects of delta-9-tetrahydrocannabinol on social behaviour in the laboratory mouse and rat. Psychopharmacologia 44(3):287-9

Cutler MG, Mackintosh JH (1984) Cannabis and delta-9-tetrahydrocannabinol. Effects on elements of social behaviour in mice. Neuropharmacology 23(9):1091-7

Sieber B, Frischknecht HR, Waser PG (1982) Behavioural effects of hashish in mice in comparison with other psychoactive drugs. Gen Pharmacol 13(4):315-20

Ham MT, De Jong Y (1975) Absence of interaction between delta9-tetrahydrocannabinol (delta-THC) and cannabidiol (CBD) in aggression, muscle control and body temperature experiments in mice. Psychopharmacologia 41(2):169-74

Cutler MG, Mackintosh JH, Chance MR (1975) Behavioural changes in laboratory mice during cannabis feeding and withdrawal. Psychopharmacologia 44(2):173-7

van Ree JM, Niesink RJ, Nir I (1984) delta 1-Tetrahydrocannabinol but not cannabidiol reduces contact and aggressive behavior of rats tested in dyadic encounters. Psychopharmacology (Berl) 1984;84(4):561-5

McDonough JH Jr, Manning FJ, Elsmore TF (1972) Reduction of predatory aggression of rats following administration of delta-9-tetrahydrocannabinol. Life Sci I 11(3):103-11

Kilbey MM, Moore JW Jr (1973) Delta9-tetrahydrocannabinol induced inhibition of predatory aggression in the rat. Psychopharmacologia 31(2):157-66

Sieber B (1982) Influence of hashish extract on the social behaviour of encountering male baboons (Papio c. anubis). Pharmacol Biochem Behav 17(2):209-16

Levett A, Saayman GS, Ames F (1977) The effects of Cannabis sativa on the behavior of adult female chacma baboons (Papio ursinus) in captivity. Psychopharmacology (Berl) 1977 Jun 6;53(1):79-81

Sassenrath EN, Chapman LF (1976) Primate social behavior as a method of analysis of drug action: studies with THC in monkeys. Fed Proc 35(11):2238-44

Cherek DR, Roache JD, Egli M, Davis C, Spiga R, Cowan K (1993) Acute effects of marijuana smoking on aggressive, escape and point-maintained responding of male drug users. Psychopharmacology (Berl) 111(2):163-8

Sulcova E, Mechoulam R, Fride E (1998) Biphasic effects of anandamide. Pharmacol Biochem Behav 59(2):347-52

Sethi BB, Trivedi JK, Kumar P, Gulati A, Agarwal AK, Sethi N (1986) Antianxiety effect of cannabis: involvement of central benzodiazepine receptors. Biol Psychiatry 21(1):3-10

Carlini EA, Lindsey CJ, Tufik S (1977) Cannabis, catecholamines, rapid eye movement sleep and aggressive behaviour. Br J Pharmacol 61(3):371-9

Carlini EA, Masur J (1969) Development of aggressive behavior in rats by chronic administration of Cannabis sativa (marihuana). Life Sci 8(11):607-20

Monti JM, Carlini EA (1975) Spontaneous behavior and sleep-wakefulness cycle in isolated and paired REM sleep deprived-marihuana treated rats. Pharmacol Biochem Behav 3(6):1025-9

Musty RE, Lindsey CJ, Carlini EA (1976) 6-Hydroxydopamine and the aggressive behavior induced by marihuana in REM sleep-deprived rats. Psychopharmacology (Berl) 48(2):175-9

Carlini EA, Gonzales C (1972) Aggressive behaviour induced by marihuana compounds and amphetamine in rats previously made dependent on morphine. Experientia 28(5):542-4

Spencer DJ (1970) Cannabis induced psychosis. Br J Addict Alcohol Other Drugs 65(4):369-72

Palsson A, Thulin SO, Tunving K (1982) Cannabis psychoses in south Sweden. Acta Psychiatr Scand 1982 Oct;66(4):311-21

Roy-Byrne PP, Uhde TW (1988) Exogenous factors in panic disorder: clinical and research implications. J Clin Psychiatry 49(2):56-61

Lion JR (1975) Conceptual issues in the use of drugs for the treatment of aggression in man. J Nerv Ment Dis 160(2-1):76-82