Cannabis Inquiry

With the upcoming Referendum on legalisation of cannabis in 2020, we ask that the government first investigate the possible link between cannabis and violence.

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Thank you for signing our petition calling on the government to investigate the possible link between cannabis and violence.

We intend to present this petition to Parliament in early July.

Please encourage as many people as possible to sign our petition. Send them to where all the details are.

Big Marijuana has high hopes for New Zealand, but liberalising marijuana laws is the wrong path to go down if we care about public health, public safety, and about our young people.

Thank you for being part of our important campaign.

Bob McCoskrie
Family First NZ


Over the past couple of decades, studies around the globe have found that THC – the active compound in cannabis – is strongly linked to psychosis, schizophrenia, and violence. A certain percentage of people who use marijuana can become psychotic and violent. Researchers have studied alcohol and violence for generations, proving that alcohol is a risk factor for domestic abuse, assault and even murder. Far less work has been done on cannabis.

It raises an important question – is our relatively higher use of cannabis compared to other countries related to our horrific record when it comes to child abuse and family violence?

In 2018, researchers at Ohio and Tennessee Universities found that marijuana use was positively and significantly associated with psychological, physical, and sexual intimate partner violence, after controlling for alcohol use and problems, antisocial personality symptoms, and relationship satisfaction. The researchers say that treatment of men arrested for domestic violence should consider reducing their marijuana use.

A 2017 paper in the journal Social Psychiatry and Psychiatric Epidemiology, examining drivers of violence among 6,000 British and Chinese men, found that drug use was linked to a fivefold increase in violence, and the drug used was nearly always cannabis.

Research published in 2016 in the journal Psychological Medicine concluded that continued use of cannabis causes violent behaviour as a direct result of changes in brain function that are caused by smoking weed over many years. The results showed that continued cannabis use is associated with 7-fold greater odds for subsequent commission of violent crimes.

A University of Florida study published in The Journal of Interpersonal Violence in 2011 found that frequent marijuana users in adolescence are twice as likely to engage in domestic violence as young adults.  The same study showed this group were more than twice as likely to become a victim of domestic violence. The researchers said “These findings have implications for intimate partner violence prevention efforts, as marijuana use should be considered as a target of early intimate partner violence intervention and treatment programming.”

A 2007 paper in the Medical Journal of Australia looked at 88 defendants who had committed homicide during psychotic episodes. It found that most of the killers believed they were in danger from the victim, and almost two-thirds reported misusing cannabis – more than alcohol and amphetamines combined.

A 2002 study in BMJ (formerly the British Medical Journal) found that people who used cannabis by age 15 were four times as likely to develop schizophrenia or a related syndrome as those who’d never used. Even when the researchers excluded children who had shown signs of psychosis by age 11, they found that the adolescent users had a threefold higher risk of demonstrating symptoms of schizophrenia later on. The study was based on the Dunedin multidisciplinary health and development study.

Some evidence is already appearing in New Zealand. Last year (2018), a man who stalked several women during a 24-hour drug-induced psychosis has left one of his victims with ”a lasting fear”. He lost his job after failing a drug test and then embarked on a four-day cannabis binge. The judge said that resulted in a psychosis. In 2017, a man repaid a family who had taken him in by stabbing the mother, a babysitter and their pet dog in a drug-induced rage. The judge said that his consumption of cannabis, which may have been laced unknowingly with methamphetamine, had caused him to attack.

Paranoia and psychosis can make some people dangerous, so a rising use of a drug that causes both would be expected to increase violent crime, rather than reduce it as drug advocates might claim.

Of the four US states that legalised marijuana in 2014 and 2015 – Oregon, Washington, Alaska, and Colorado – there was a combined 35% increase in murders in those states from 2013 to 2017, compared with a 20% rise nationally. Washington became the first U.S. jurisdiction to legalise recreational marijuana in 2014. Between 2013 and 2017, the state’s aggravated-assault rate rose 17%, which was nearly twice the increase seen nationwide, and the murder rate rose 44%, which was more than twice the increase nationwide.

Here in New Zealand, we know from a number of governmental reports (UNICEF reports in 2003and 2007, a CYF report in 2006, and a Children’s Commissioner report in 2009) that one of the factors most commonly associated with the maltreatment of children is drug abuse.

In March, Texas released its report on child abuse deaths, finding half the 172 child abuse deaths in 2017 coupled with substance abuse.  Marijuana was the most-used substance connected to child abuse and neglect deaths, followed by alcohol, cocaine and methamphetamine. In one terrible case last year, Cynthia Randolph left her 1-year old and 2-year-old in the car while she smoked pot. Both children died.

In 2017, Arizona also published a report showing that marijuana was the substance most often linked to child abuse deaths in 2016.


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