Smoking cannabis is endangering young people’s mental health more than ever before – because it’s stronger, according to new research.
Modern marijuana contains more THC (tetrahydrocannabinol) – the psychoactive ingredient that produces the ‘high’.
It’s putting teenagers, in particular, at increasing risk of hallucinations, paranoia and other psychotic problems, two studies show today (Monday).
They are two-and-a-half times more likely to develop dependence – or cannabis use disorder – within a year of first taking the drug.
It should prompt 10 states and Washington DC – where recreational use has been made legal – to reconsider, say US scientists.
Professor Brooke Arterberry, a psychologist at Iowa State University, said: “THC has linearly increased over two decades.
“Based on the results, states may want to think about the available potency levels of cannabis products – especially with the changing legal landscape of cannabis.”
Another study of 14 to 18 year-olds found those with cannabis use disorder were more likely to suffer hallucinations or paranoia.
Corresponding author Prof Sharon Levy, a paediatrician at Boston Children’s Hospital, said: “Respondents who met criteria for cannabis use disorder were more likely to report having experienced hallucinations or paranoia.”
Earlier this year an analysis of almost 1,000 samples seized by police found most cannabis being sold illegally in the UK is super-strength skunk.
This has much more THC than some other types of cannabis – such as hash resin.
There are three main types of street cannabis – hash (hashish or resin), herbal cannabis (weed, grass or marijuana) and high-potency cannabis or skunk.
Hash is made from the resin of the plant, while herbal cannabis is made from the dried leaves and flowering parts of pollinated cannabis plants.
Skunk is made from from unpollinated cannabis plants which naturally contain higher levels of THC – the substance that gives recreational users the ‘stoned’ feelings they seek from the drug.
But it can also cause nasty side effects – including paranoia and hallucinations.
Hash and herbal cannabis are considered to be milder than skunk. That’s because they contain higher levels of a substance called CBD (cannabidiol) which experts say works as an anti-psychotic and counteracts some of the negative effects of THC.
It’s argued that cannabis with high levels of THC and no or very low CBD can lead to people developing psychiatric issues.
Prof Arterberry and colleagues found individuals who used lower potency cannabis (4.9%) were 1.88 times more likely to develop dependency symptoms in 12 months.
This rose to almost fivefold (4.85 times) for those whose those whose first cannabis had a potency of 12.3 percent – in line with most of the drug today.
The researchers said the finding published in Drug and Alcohol Dependence is a “concern given THC has increased significantly” – from 3.5 percent in 1994 to 12.3 percent in 2012.
It was based on long running drink and drugs data from people in Michigan who were followed between the ages of 11 and 26.
This included in-depth assessments at three-year intervals and annual questionnaires about cannabis use.
Only those participants who started using cannabis between 1994 and 2012 were included.
It could provide an opportunity for early intervention and prevention, said Prof Arterberry.
Symptoms of the disorder may include craving or strong desire to use cannabis, recurrent use in situations in which it is physically hazardous or failing to meet obligations at work, home or school.
Prof Arterberry said there are many similarities between cannabis and alcohol use disorders – but we don’t know as much about the former.
For example, alcohol is sold based on volume and there is a specific blood alcohol level for impairment.
However, there are no regulations or limits on potency in states where medical or recreational cannabis is legal.
Prof Arterberry said some concentrates have THC levels of up to 80 percent – and people may not understand the potential risks linked to different levels.
Other potential harms include increased car crashes and other accidents due to impairment through taking cannabis.
The problem is researchers do not know what constitutes “safe levels” of THC. Prof Arterberry said and until this is established it is difficult to create effective policies.
She would like to see future research focus on potency of individual cannabis used – rather than national average levels.
Prof Arterberry said: “This is the first step toward understanding the influence of potency.
“While more research is needed, the risk associated with higher potency highlights the need for early intervention and targeted prevention efforts.”
The second study published in JAMA Pediatrics based on 527 found 146 said they had used cannabis in the past year.
Overall, 40 (27.4%) reported hallucinations, 49 (33.6%) paranoia or anxiety – and 63
(42.9%) reported having at least one psychotic symptom.
Prof Levy said: “Seventy respondents (47.9%) affirmed ‘monthly or more’ marijuana use during the past year – and this group was more likely to report experiencing hallucinations and paranoia compared with youths who affirmed use ‘once or twice’
in the past year (42 [60.0%] vs 28 [40%]).”
She added: “Our findings suggest that experience of marijuana-related acute psychotic symptoms may be considerable.”
Three years ago King’s College London researchers found smoking super-strength cannabis can cause significant levels of damage to ‘white matter’ called the corpus callosum.
This carries signals between the brain’s left and right sides. Disruption can lead to mental illnesses and psychotic symptoms such as hallucinations, as well as slowing down the brain’s activity.
Skunk is the most popular type of cannabis in the UK.
In February another King’s College London team found 94% of police seizures of cannabis in 2016 were high-potency varieties – compared to 85% in 2008 and 51% in 2005.
By Mark Waghorn