Opioids v medicinal cannabis: Which is the better option?

In April, the medicinal cannabis scheme took effect, allowing GPs to prescribe the drug to patients. Some GPs are wary of medicinal cannabis, due to a lack of evidence-based research. However, medicinal cannabis is thought to be an alternative to opioids, a drug with "harmful" effects.

"We need to understand where the drug [cannabis] is of use and where it is not," Dr Bryan Betty, medical director of RNZCGP told Newshub.

"There is a growing awareness of the harmful effects [of opioids] and this is always at the front of a GP's mind." 

Here Newshub looks at some of the issues surrounding these drugs. Although cannabis is slowly becoming legal throughout the world, the evidence surrounding its uses is sparse. The studies presented in this article are mostly from areas in the United States which treat cannabis as a controlled substance.

Graphic pull quote which reads: "There is a growing awareness of the harmful effects of opioids, and this is always at the front of a GPs mind."

How many fatalities have these drugs caused in New Zealand?

The Drug Harm Index measures drug-related deaths using data from the United Nations Office on Drugs and Crime. A certain number of deaths are allocated to each drug per year, to calculate "personal harm". These figures are not a record of every individual whose cause of death may have been drug-related, but an average. These deaths include people who had a fatal accident or injury with drugs in their system, but drugs were not the direct cause.


A toxic dose of opioids can cause respiratory failure. In the Drug Harm Index, 10 deaths are allocated to opioids annually, while coronial figures suggest this figure is closer to 38. The Drug Foundation suggests the low allocation "dramatically underplays the number of deaths and related harm for this group of substances".


According to the New Zealand Drug Harm Index, cannabis is responsible for 32 deaths a year. This number is reflective of the harm caused by cannabis, which can have a significant impact on a chronic user's mental health. It is widely understood there is no toxic dose of cannabis. The Drug Foundation believes a toxic overdose should be the only definition used to count drug-related deaths. 

"Conflating deaths where drugs were the contributing case, with deaths where drugs were a more direct cause is misleading and inaccurate," the organisation wrote on their website.

David Schmader, author of Weed: The User's Guide, says overdosing is impossible.

"A fatal dose of marijuana would require ingestion of 1500 pounds [670kg] in 15 minutes, a physical impossibility for any human," Schmader told The Next Web.

Quote from David Schmader: "A fatal dose of marijuana would require ingestion of 670kg in 15 minutes, a physical impossibility for any human."

Is this drug addictive?


US doctor Nathan Jakowski explains when opioids are taken, dopamine is released, activating the reward system within the brain.

"In drug use, this leads us to seek out the drug again and again... even short-term use of the opioid can lead to addiction," Dr Jakowski wrote in an article.

Opioids can make your brain and body believe they are necessary for survival. This happens relatively quickly, as your body develops a tolerance and craves more.


Long-term users are at risk of developing cannabis use disorder which affects 1.5 percent of American adults. US professor Dr J Wesely Boyd, told Healthline cannabis use was "potentially harmful" to those whose brains are still developing. It is understood the risk of addiction becomes greater the earlier you start using cannabis. If cannabis was to be legalised in New Zealand, use would be restricted to those aged 20 and older.

Quote from Dr Nathan Jakowski "In drug use, this leads us to seek out the drug again and again...even short-term use of opioids can lead to addiction."

What are the side effects of this drug?


The main side effect of continued opioid use is physical dependence and addiction. A quarter of opioid users report unpleasant side effects, such as constipation, nausea, sleepiness and dizziness. Long-term use of opioids can have serious consequences, such as hypogonadism, adrenal insufficiency and abnormal pain sensitivity


A report by the World Health Organisation states CBD, the non-psychoactive component of cannabis, "exhibits no effects indicative of any abuse or dependence potential". Common side effects from CBD include nausea, fatigue and irritability. Users of Sativex, the only THC-inclusive medication available in New Zealand, can experience dizziness and fatigue.

Does this drug cause anxiety or depression?


A 2011 article in the Psychiatric Times stated opioid use may cause anxiety.

"You may struggle with anxiety as a result of use, or you may struggle with drug dependence because of anxiety. These issues support one another and create an escalating cycle," co-authors Matt Kushner and Shelia Specker wrote. A 2015 study conducted by the US Annals Family Medicine found 10 percent of the patients surveyed developed depression after using opioids for a month.


Australian researcher Dr Peter Gate wrote an article for The Conversation detailing the relationship between cannabis use, anxiety and depression. Dr Gates highlighted a 2014 study done by Cambridge University, which found cannabis users had a moderate risk of developing depression. However, this study was not able to conclude cannabis was the cause of depression.  The amount of psychoactive THC in the drug may influence whether a user feels anxiety. Nora Volkow, director of the National Institute on Drug Abuse, states in an article for NPR that cannabis with low levels of THC can reduce anxiety and enhance relaxation, whereas a very potent strain can cause paranoia and panic attacks. Volkow believes the relationship between cannabis use, depression and anxiety is complex, and may affect each cannabis user differently.

Quote from Dr Barry Logan: "A user-preferred dose produces a level of impairment equivalent to a moderate level of alcohol consumption for about 2-4 hours."

Does this drug impact a person's ability to drive?


A 2018 study examined 22 people who drove under the influence of opioids. Researchers found the drug affected the subject's driving and increased sleepiness. Four people had to stop their driving test because they were too sleepy.


US doctor Barry Logan told the Drug Foundation there is no doubt cannabis impairs driving.

"A user-preferred dose produces a level of impairment equivalent to a moderate level of alcohol consumption for about 2-4 hours," Dr Logan says.

The Drug Foundation cited a study showing heavy users of cannabis may be constantly impaired for some weeks after stopping use. The study stated you are five times more likely to have an accident with cannabis in your system.