Updated 20 November 2014

Dagga is more dangerous than previously thought

A new scientific review has shown that regular marijuana smoking is related to a number of negative health consequences, including schizophrenia and heart issues.


Despite the steady relaxing of anti-drug laws surrounding cannabis, the medical community is still split on the safety of the substance. Criticisms around the safety of the drug have been re-raised following a new review, published in the journal Addiction

Among numerous other findings, the review found that teenagers who regularly smoke marijuana are twice as likely to suffer from mental disorders and impaired brain function. Schizophrenia, a severely debilitating mental disorder, has particularly been linked to heavy marijuana usage, according to the National Alliance on Mental Illness in the US.

A key study cited in the review found that 13% of schizophrenia cases could have been prevented if cannabis use was avoided, this was found in a 27-year follow-up study of over 50 000 young Swedish men.

Read: Booze and pot bad for teens

The author of the review, Professor Wayne Hall, says that the perception of cannabis as a safe drug is due to an overreaction to previous warnings about its dangers, which were greatly exaggerated, he told Live Science. Hall is professor of addiction policy at King’s College London and a drugs advisor to the World Health Organisation.

The review also found a 100% increase in car accidents amongst people who drove after smoking marijuana than those who didn’t.

Dagga smokers often argue that the drug is not addictive, another claim that was debunked by the paper. Hall went as far as to claim that the drugs is just as addictive as heroin, likely due the narcotic high it produces.

Heart problems were also touched on, with there being numerous reports of seemingly healthy people, particularly men, suffering fatal heart attacks after smoking marijuana.

This effect multiplied if subjects smoked in middle-age. However, these findings are muddied by the fact that most cannabis smokers also smoke cigarettes, which have well-documented affects on the heart.

Read: Alcohol combined with dagga turns teens lethal on the roads 

The key substance in marijuana is delta-9-tetrahydrocannabinol, usually referred to as THC. It’s this ingredient that provides the “high” of marijuana and is also believed to be at the root of the drug’s health issues, though a causal link has yet to be established. Hall reported that the THC content of marijuana has more than quadrupled since 1980.

Read: Islamic Morocco considers legalising marijuana

One of the most common arguments levelled against cannabis use is that, while it isn't dangerous in itself, it is a gateway to drugs that are. There are no reported cases of anyone dying from a marijuana overdose, and it’s a matter of scientific debate as to whether an overdose is even possible.

The review also found that smoking marijuana was related to a greatly increased likelihood of dropping out of school, and that women who smoke while pregnant are likely to give birth to babies with lower-than-average birth weight.

After years of lobbying, marijuana was legalised in two US states this year with several others likely to legalise it in the near future, it has also been decriminalised in many others. Marijuana is still illegal in South Africa, but this could be about to change.

The Medical Innovation Bill was tabled this year by IFP MP Mario Orioli-Ambrosini deals specifically with this topic, according to News24. The bill was copied from a bill of the same name currently under consideration by the UK parliament. 

Read more:

Legalising marijuana cuts drug overdose deaths 
Making pot legal could cause more problems
Students more likely to drive stoned than drunk


Read Health24’s Comments Policy

Comment on this story
Comments have been closed for this article.

Live healthier

Exercise benefits for seniors »

Working out in the concrete jungle Even a little exercise may help prevent dementia Here’s an unexpected way to boost your memory: running

Seniors who exercise recover more quickly from injury or illness

When sedentary older adults got into an exercise routine, it curbed their risk of suffering a disabling injury or illness and helped them recover if anything did happen to them.