Cannabis and Mental Illness

Early in the evening on April 14, 47-year-old Richard Kirk stopped by Nutritional Elements, a marijuana store in southeast Denver.  He bought Karma Kandy Orange Ginger, a candy form of edible marijuana, and Pre 98 Bubba Kush Pre-Roll, a pre-rolled joint.  Three hours later, at home, he shot his wife Kristine in the head.  At the time she was on a call with a 911 dispatcher.  During her 13-minute call, she reported that Richard was hallucinating, talking about the end of the world, and asking her to shoot him.  She and their three young boys were frightened.  Still on the line, she started screaming when she saw her husband returning from a safe with a handgun.  In his bedroom, their 7-year-old son heard a gunshot, and the screaming stopped.  Minutes later, his father walked in and asked the boy to kill him so that “Dad and Mom could be together with God.”  In custody later that evening, Richard asked if he could call his wife and three sons.  He wanted to explain that the “blood moon” was causing his mood swings.  Cannabis

On January 1, 2014, Colorado became the first state to permit the sale and use of marijuana for recreational purposes.  The road to legalization was an occasion for argument between those who feared a consequent rise in crime and those who saw no link between marijuana use and crime.  In late March of this year, the latter group found support in research out of the University of Texas at Dallas which, finding that medical marijuana legalization may be correlated with a decrease in homicide and assault rates, has received wide attention.

Kristine Kirk’s murder and the University of Texas research rekindled the dialogue concerning the link, or lack thereof, between cannabis and crime.  Often missing from this conversation, however, is discussion of the risks of cannabis use by the mentally ill.  According to one recent report, evidence suggests that, when used frequently, cannabis is associated with an increased risk of psychosis.  Another study finds that early cannabis use is associated with psychosis-related outcomes in young adults.

Reports of adverse reactions to marijuana are apparently up.  The Medical Director of the Rocky Mountain Poison and Drug Center said the center had received 65 calls about adverse reactions within the first four months of 2014, compared to 126 throughout 2013.  He attributed the increase to higher concentrations of THC in commercially available marijuana.  He noted that violence is possible depending on the type of hallucinations a user experiences.  Separately, there have been reports of a jump in the number of young children brought to hospitals after eating marijuana packaged to look like candy.

Comment by Avram Mack, M.D.

Cannabis is a substance that is associated with problematic effects in several domains of human mental functioning. When a good investigation into the basis of human behavior is needed, it is essential not to overlook the many potential mechanisms by which cannabis could cause or be associated with violence or aggression.  Contrary to its image as a sedating or relaxing substance, in some individuals the effects could foment violence or aggression through anxiety, mis-perceptions, or agitation or by its negative impact on thinking, intelligence, or judgment.  Good forensic mental health experts will duly explore the effects of cannabis on the individual within the context of the individual’s overall state.

On a side note, the increased availability of cannabis poses the potential for an increase in involuntary intoxication defenses.  Individuals may be unintentionally given food with cannabis baked or cooked into it.  And, for individuals who are involuntarily exposed to such food or who are exposed to heavy smoke from nearby users, there is also a risk of testing “positive” on urine drug tests.  Forensic addiction experts can assist in interpreting such “false positive” results.


1.     Steffen, Jordan, “Recordings capture police response to woman killed while on 911 call,” The Denver Post, Apr. 16, 2014. Web Apr. 24, 2014.

2.     Steffen, Jordan, “Woman killed in Observatory Park home said husband ate pot candy,” The Denver Post, Apr.17, 2014. Web Apr. 24, 2014.

3.     Martinez, Michael, et al., “Colorado woman shot dead while on phone with 911 for 13 minutes,” CNN, Apr. 17, 2014. Web Apr. 24, 2014.

4.    Steffen, J. “Richard Kirk hearing: Suspect asked boy, 7, to kill him,” The Denver Post, 22 Aug. 2014.  Web. 22 Aug. 2014.

5.     Stack, Liam, “Colorado Counts Down to Legalized Marijuana Use,” The New York Times, Dec. 31, 2013. Web Apr. 24, 2014.

6.     Compare, e.g., Ferner, Matt, “After 3 Months Of Legal Pot Sales, Denver Still Not A Crime-Filled Hellscape,” The Huffington Post, Apr. 7, 2014, Web Apr. 24, 2014, with “Sheriff In California Says Coloradans Will Regret legalizing Marijuana,” CBS Denver, Feb. 11, 2013. Web Apr. 24, 2014.

7.     Morris, R.G., et al., “The Effect of Medical Marijuana Laws on Crime: Evidence from State Panel Data, 1990-2006.” PLoS ONE 9(3): e92816 (2014).

8.    Lynch, M. “The Cannabis-Psychosis Link,” Psychiatric Times, 12 Jan. 2012.

9.    McGrath, J., et al., “Association Between Cannabis Use and Psychosis-Related Outcomes Using Sibling Pair Analysis in a Cohort of Young Adults,” Arch Gen Psychiatry, 67:5, published online 1 Mar. 2010.

10.   Gurman, Sadie, “Colorado deaths stoke worries about pot edibles; lawmakers move to tighten rules,” US News & World Report, Apr. 18, 2014. Web Apr. 24, 2014.

11.   Ingold, John. “Children’s Hospital sees surge in kids accidentally eating marijuana,” The Denver Post, 21 May 2014.  Web. 22 Aug. 2014.