The risk of developing psychosis as a result of smoking cannabis is much lower than first thought, scientists believe.
Over the years, a host of previous research has pointed to a link between the popular recreational drug and mental health conditions.
But a new review of existing studies published yesterday on 4/20, an unofficial day to celebrate cannabis, has found that cases are relatively rare.
However, those who smoke high amounts of weed should still be careful, York University researchers said.
But a new review of existing studies published on 4/20, an unofficial day to celebrate cannabis, has found that it’s relatively rare for weed to cause any such symptoms
Lead author Ian Hamilton, a lecturer in mental health, said the greatest danger cannabis users face is by combining the drug with tobacco.
He pointed to previous British research that showed to prevent just one case of psychosis, 23,000 people who have to stop using the class B drug.
Mr Hamilton told The Independent: ‘The link between cannabis and psychosis has been investigated by researchers since the drug became popular in the 1960s.
‘A new review of research carried out since then has concluded that ‘at a population level the increased risk is weak and the vulnerabilities relatively rare’.’
His review, published in the journal Addiction, stated more research was needed on the impact of high potency cannabis.
But he said the studies clearly showed that the stronger the weed, the more likely someone is to develop mental health problems.
Over the years, a host of previous research has pointed to a link between the popular recreational drug and mental health conditions
He said most of the high profile studies that have been conducted are from a time when lower strength strains were the norm.
High potency cannabis contains less of cannabidiol (CBD), which is believed to protect against negative side-effects, such as psychosis.
While it has a higher level of tetrahydrocannabinol (THC) – the component in the drug that causes the high effect – l that can trigger the symptoms.
Marijuana has become far more potent over the past 20 years, scientists revealed last February.
A study analysed nearly 39,000 samples of cannabis seized by the US Drug Enforcement Administration between 1995 and 2014.
The levels of the component responsible for marijuana’s psychedelic effects – called tetrahydrocannabinol, or THC – ‘consistently increased’ during that time.
THC levels in the confiscated weed grew from four per cent in 1995 to 12 per cent in 2014.
The study said: ‘This increase in potency poses higher risk of cannabis use, particularly among adolescents.’
Marijuana is the most widely used illicit drug in and worldwide, the University of Mississippi researchers added.
The review also showed for the first time there is sufficient evidence to demonstrate that for patients who already have schizophrenia, cannabis makes symptoms worse.
Psychosis is defined as a form of mental illness where people experience delusions, hallucinations, or both at the same time.
Associated with conditions such as schizophrenia and bipolar disorder, some victims are so badly affected that they end up committing suicide or seriously harming others because they believe they are being ordered to do so by voices in their heads.
Regulating cannabis, used by more than two million people in England and Wales in the past 12 months, would help to reduce any health risks that the drug can pose, Mr Hamilton added.
He said: ‘A regulated cannabis market would introduce some quality control.
‘This would provide users with information about the strength of cannabis on offer, something they usually only discover after exposure in the current unregulated market.’
Super-strength strains of cannabis are responsible for up to a quarter of new cases of psychotic mental illness, scientists warned two years ago.
The potent form of the drug, known as ‘skunk’, is so powerful that users are three times more likely to suffer a psychotic episode than those who have never tried it, King’s College London researchers found.