World's biggest marijuana study: so is weed bad?

So is smoking weed really bad for you?
So is smoking weed really bad for you?

WHILE the recreational use of marijuana is becoming slowly legalised across the globe, the drug is still largely considered to have diminishing results on mental and physical health.

But how much of this view is based on fact and how much is derived from weed-fearing propaganda from days gone?

To try to answer that question, the National Academies of Sciences, Engineering and Medicine recently completed the world's most comprehensive study into marijuana, which examined more than 10,000 scientific abstracts dating back to 1999.

"This report summarises the current state of evidence regarding what is known about the health impacts of cannabis and cannabis-derived products, including effects related to therapeutic uses of cannabis and potential health risks related to certain cancers, diseases, mental health disorders, and injuries," the report read.

The extensive 395-page report unearthed more than 100 conclusions about the health effects of recreational and therapeutic cannabis use, with many bound to make people question their stance on the natural plant.

Here are some of the more thought-provoking finds.

Generic image of cannabis.
Generic image of cannabis. Bill North

The report said that smoking cannabis on a regular basis is associated with chronic cough and phlegm production, but says quitting smoking or ingesting the drug orally will likely reduce these symptoms.

"The evidence suggests that smoking cannabis does not increase the risk for certain cancers (i.e., lung, head, and neck) in adults," the report read.

"There is modest evidence that cannabis use is associated with one subtype of testicular cancer.

"There is minimal evidence that parental cannabis use during pregnancy is associated with greater cancer risk in offspring.

"Smoking cannabis on a regular basis is associated with chronic cough and phlegm production.

"It is unclear whether cannabis use is associated with COPD [chronic obstructive pulmonary disease], asthma, or worsened lung function."

Saliva Testing for cannabis
Saliva Testing for cannabis contributed


With medicinal use of marijuana becoming more widespread, there is more evidence supporting the therapeutic effects of weed - something this study confirmed.

"In adults with chemotherapy-induced nausea and vomiting, oral cannabinoids are effective antiemetics," the report read.

"In adults with chronic pain, patients who were treated with cannabis or cannabinoids are more likely to experience a clinically significant reduction in pain symptoms.

"In adults with multiple sclerosis (MS)-related spasticity, short-term use of oral cannabinoids improves patient reported spasticity symptoms."

When looking at the effects of cannabis or cannabinoid-based therapeutics on the human immune system, the researchers said there is insufficient data to draw overarching conclusions.

However, the report claims there is "limited evidence to suggest that regular exposure to cannabis smoke may have anti-inflammatory activity."

Generic image of cannabis.
Generic image of cannabis. Bill North


When looking at cannabis use and mental health, the findings offer mixed results.

"Cannabis use is likely to increase the risk of developing schizophrenia and other psychoses; the higher the use the greater the risk," the report read.

However, it added that a history of cannabis individuals with schizophrenia and other psychoses may be "linked to better performance on learning and memory tasks".

The research found smoking weed did appear to increase the likelihood of developing depression, anxiety or PTSD, with heavy cannabis smokers even more likely to report thoughts of suicide than non-users.

Users with bipolar disorders should refrain from smoking too frequently.

"For individuals diagnosed with bipolar disorders, near daily cannabis use may be linked to greater symptoms of bipolar disorder than non-users," the report read.

The Federal Government has moved to legalise medical marijuana, with the onus now on the State Governments to follow suit.Photo Cathy Adams / The Northern Star
The Federal Government has moved to legalise medical marijuana, with the onus now on the State Governments to follow suit.Photo Cathy Adams / The Northern Star Cathy Adams


The effects of marijuana use is proven to have some diminishing effects for mental capacity, with adolescents worse off.

"Cannabis use during adolescence is related to impairments in subsequent academic achievement and education, employment and income, and social relationships and social roles," the report read.

The same held true for adults, with findings stating that "recent cannabis use impairs the performance in cognitive domains of learning, memory, and attention."

However, it mentioned these findings were only present in evaluations 24 hours after use.


There has been zero recorded deaths from overdosing on marijuana, although the report does suggest it could play a role in other fatal injuries from being stoned.

"Cannabis use prior to driving increases the risk of being involved in a motor vehicle accident," the report read.

As for addiction, heavy use can be habit forming and could also lead to the abuse of other substances.

"Greater frequency of cannabis use increases the likelihood of developing problem cannabis use," the report read.

"Initiating cannabis use at a younger age increases the likelihood of developing problem cannabis use.

"Cannabis use is likely to increase the risk for developing substance dependence (other than cannabis use disorder).

Topics:  editors picks marijuana medicinal marijuana study weed

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