Cannabis is generally classified among the so-called soft drugs, those which are socially accepted and perceived as less harmful, such as tobacco or alcohol. However, there are no harmless drugs. All have an impact on physical and mental health and carry a high risk of addiction. However, scientists have attempted to determine the threshold that triggers the actual risk; in the case of cannabis, researchers from the Hospital Clínic and the Institute for Biomedical Research August Pi i Sunyer (IDIBAPS), in Barcelona, Spain, have reached a scientific consensus that five or more joints of marijuana or of hashish per week are considered harmful.
According to the World Health Organization (WHO), around 147 million people (2.5% of the world’s population) use cannabis. It is by far the most cultivated, most trafficked and most used illicit substance; cocaine or opiates, by comparison, are used by about 0.2% of the world’s population. And even if it is described as a soft drug, and despite its therapeutic effects – to treat nausea and vomiting at an advanced stage of cancer or AIDS, for example – its harmful effects are numerous: it alters cognitive development, memory, psychomotor functions and attention span, and it can cause respiratory damage, among other damage.
Mercé Balcells, head of the addictive behaviors unit at the Hospital Clínic and member of the group that reached this consensus, stressed that cannabis use is by no means harmless. “There is no zero risk. You might smoke a joint for the first time today and have a panic attack, for example. You can be a healthy person, smoke a joint, and things can happen to you. I can’t tell you that nothing will happen to you. It’s a substance that gets to your brain,” she said.
A man rolls a joint.Leonardo Álvarez Hernández (Getty Images)
Beyond each particular case, in the field of public health, a pattern of risky consumption is generally established, a tipping point after which the risk of having a problem related to the consumption of a substance increases exponentially. . With alcohol, for example, it’s 20 grams a day for men (two glasses of wine) and 10 grams for women. With cannabis, according to the researchers, who presented the results at a scientific conference in Granada, it’s five or more joints per week.
Balcells pointed out that quantity is considered when measuring risk, but so is frequency. She explains that there has been a certain social trivialization of the risks of cannabis, and warns of its complexity: “We tend to present it as something benign, natural… But the fact that it comes from a plant does not prevent This means that it will not affect health.
The strength of cannabis is also a key element in calculating the risk, adds the specialist. “In 2014, we defined a standard common unit and looked at the amount of THC, which is the cause of harm. The potency of marijuana is important: if it is above 10%, it is risky consumption”, she said. However, she admitted that it is “difficult” for users to know how much THC is in their joint. “What we are seeing now is that the potential of what is distributed increases. Before, a few years ago, there was a lesser amount, “she warned. More THC means more addiction and a greater risk of mental health disorders like psychosis, or a earlier onset of other illnesses such as schizophrenia.
Highly vulnerable groups
Balcells also pointed out that there are particularly vulnerable populations, such as people under the age of 21, pregnant women, nursing mothers or people with underlying physical or mental conditions. For these groups, any consumption, however limited or occasional, poses a health risk. “Consuming at an early age lowers IQ and produces cognitive impairments.”
The new consensus is in line with that reached by Canadian researchers, who first recommend total abstinence to reduce risk. These experts pointed out that an early onset – consuming before the age of 16 – is associated with “multiple subsequent adverse health and social effects in the lives of young adults”, especially if consumption is also frequent. They also considered that “people predisposed to psychosis and substance use disorders, or with a first-degree family history, as well as pregnant women (mainly to avoid adverse effects on the fetus or new -né)” were particularly vulnerable to the risks of cannabis.
Sign up for our weekly newsletter to get more English language news coverage from EL PAÍS USA Edition
