Cannabis is popularly placed on the team of the (mis)called soft drugs, those that are socially accepted and perceived as less harmful.
Like tobacco or alcohol.
But there is no harmless drug.
Neither soft nor hard.
All have an impact on physical and mental health and impose a high risk of dependency on them.
There is no 100% safe consumption in any of the cases, but scientists have tried to refine how much triggers, without a doubt, the risk to health.
With regard to cannabis, researchers from the Hospital Clínic de Barcelona and IDIBAPS have coordinated a scientific consensus that amounts to five or more joints of marijuana or hashish per week as the dose that is harmful to the body.
Around 147 million people, 2.5% of the world's population, use cannabis, according to the World Health Organization (WHO).
It is, by far, the most cultivated, trafficked and consumed illicit substance, above cocaine or opiates, which are taken, for example, by around 0.2% of the world's population.
And although it is called a soft drug, and therapeutic effects have even been described —to treat nausea and vomiting in advanced stages of cancer or AIDS, for example— its harmful effects on health are in the dozens: it impairs cognitive development, memory, psychomotor function, attention span and can cause respiratory lesions, among other damages.
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Mercé Balcells, head of the Clínic's addictive behaviors Unit and member of the working group that has drawn up the consensus, points out that cannabis use is by no means harmless.
“Zero risk does not exist.
You smoke a joint today for the first time and you may have a panic attack, for example.
You can be a healthy person, smoke a joint and have things happen to you.
And I can't tell you that nothing will happen to you.
It is a substance that reaches your brain, ”she explains.
In the field of public health, however, beyond each particular case, a pattern of risk consumption is usually established.
That is, the inflection point from which the risk of having a problem related to the consumption of a substance grows exponentially.
With alcohol, for example, it is 20 grams a day for men (two glasses of wine) and 10 grams for women.
In cannabis, according to the Clínic working group, which has presented the results at a scientific conference in Granada, five or more joints a week.
Balcells points out that quantity, but also frequency, influences when measuring risk: 3.7% of Spaniards use cannabis daily or almost daily, which implies that they have a high-risk consumption pattern for health.
The expert admits to a certain social trivialization of the risks of cannabis and warns of its complexity: "There is a tendency to present it as something risk-free, natural... But the fact that it comes from a plant does not mean that it will not have repercussions on health."
A man makes himself a marijuana joint. Leonardo Álvarez Hernández (Getty Images)
The potency of cannabis is also a key element in calculating risk, adds the specialist.
“In 2014 we defined a standard joint unit and looked at the amount of THC, which is what develops the damage.
The potency of marijuana will be important: if it is more than 10%, it is risky consumption ”, she adds.
But it is “difficult” for users, she admits, to know how much THC is in their joint: “What we see now is that the potential of what is distributed is increasing.
Before, a few years ago, I had less quantity in the preparation, ”she warns.
A higher THC load means more addictiveness and a greater risk of mental health disorders, such as psychosis, or an earlier onset of other ailments, such as schizophrenia.
Very vulnerable groups
Balcells also highlights that there are especially vulnerable populations, such as those under 21, pregnant women, nursing mothers or people with underlying physical or mental pathologies.
For these groups, any consumption, however small or infrequent it may be, already poses a health risk.
"Consumption at an early age decreases the IQ and produces cognitive alterations."
The scientific consensus acquired is in line with that agreed by Canadian researchers, which begins by recommending total abstinence to reduce the risks that cannabis has on health.
From there, experts from Canada point out that the early onset of consumption -before the age of 16- is associated "with multiple adverse social and health effects later in young adult life", especially if, in addition to early, consumption is intensive.
Canadians also consider populations especially vulnerable to the risks of cannabis to be “persons with a predisposition or a first-degree family history of psychosis and substance use disorders, as well as pregnant women (mainly to avoid adverse effects on the fetus or newborn). ”.
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