Eleven years after Jamaica decriminalised ganja, the use of the substance features heavily among patients presenting with psychosis and schizophrenia. While there is currently no data establishing whether use of the herb is causing or contributing to the mental health problems, its prevalence is complicating treatment.

This is against the background of data from the National Council on Drug Abuse (NCDA) pointing to an increase in high-risk usage of cannabis and the potency of the substance in Jamaica, as well as an increase in admissions for psychosis and schizophrenia over the last decade.

“What we do know is that the majority of psychiatric admissions in our public hospitals are coming from psychosis or schizophrenia. And the majority of those persons do use cannabis. So, we can look at that relationship and see that it is strong,” said Director for Treatment Services at the NCDA, Dr Kristen Robinson Barrett.

Still, Robinson Barrett noted that there is little data specifically exploring cannabis-induced psychosis.

Psychiatrist at Bellevue Hospital, Dr Brian Kazaara concurred that cannabis use has a striking presence among patients presenting with mental issues, but suggested that the substance rarely causes psychotic disorders.

“We don’t have official studies performed at Bellevue Hospital regarding cannabis use among patients, but from a cursory observation I can safely say the vast majority of patients admitted to the hospital also use cannabis,” he said.

Kazaara, who previously worked at the University Hospital of the West Indies (UHWI), pointed to a survey carried out by UHWI that revealed that the majority of persons admitted to the institution’s psychiatric ward smoked cannabis.

“What studies show is that persons with common psychiatric conditions like major depressive disorder or anxiety disorders use cannabis far more frequently than persons who do not have mental illnesses,” he said.

Despite this, Kazaara explained, “Cannabis-induced psychosis is not the norm. It is rare. At Bellevue we very, very rarely see that diagnosis. I also worked at UHWI for seven years [and] rarely saw it, almost never.”

Cannabis is a psychoactive drug and can affect the way that people perceive the world, leading to relaxation, paranoia, or other effects.

“It binds to our cannabinoid receptors around our body, but particularly in our brain, and that’s how we get the effects. It tends to create effects as it relates to emotions and feelings,” Robinson Barrett said. “They might experience changes as it relates to their time perception, so things might feel slowed down… issues with their concentration, so their attention and their awareness, their reaction time will change.”

Kazaara cautions that cannabis use can muddle the treatment of mental health issues.

“Cannabis definitely complicates psychosis, because for persons who use cannabis, they are more likely to develop an earlier onset of psychosis. So it may happen earlier than if they didn’t use it. It makes symptoms worse. It makes it harder to treat,” he explained.

Jamaica has a strong culture of recreational cannabis use, and Research Analyst at the NCDA Uki Atkinson explained that while overall population use has not necessarily changed over the last decade following decriminalisation of the drug, the potential for high-risk use has.

She supported her assessment with results from the Cannabis Abuse Screening Test (CAST) which was used during surveys in 2016 and 2023.

“We were able to compare the levels of high-risk use from 2016 to 2023. In 2016, 50 per cent of the people who used cannabis in the past year were deemed to be at high risk for misusing it,” Atkinson said, noting “this has increased by 16 per cent in 2023. So, it shows not necessarily that more people are using ganja… But there’s a significant increase in high-risk patterns of use.”

In addition to high-risk usage, the potency of cannabis being consumed in Jamaica is also a concern.

According to a European study, using high-potency cannabis with a tetrahydrocannabinol (THC) concentration over 10 percent, significantly increases the risk of developing psychotic symptoms or disorders, especially with daily use.

Robinson Barrett expressed serious concern about current potency trends worldwide compared to a potency of around four per cent in the 1990s.

“As of 2024, we’re looking at potencies of 15 to 20 per cent,” Robinson Barrett indicated.

“The potency trends of cannabis in Jamaica measured between 2014 and 2020, were showing that over that decade, the cannabis potency would have moved from about one per cent to over 10 per cent across 12 parishes,” she continued. “So, we’re concerned… because we have a culture of heavy use in young age groups…it’s a very concerning picture as it relates to all young people and any other vulnerable group.”

Outside of general risks, Robinson Barrett noted that there are some who may be particularly susceptible to the effects of cannabis use, including youth.

“Generally speaking, the earlier the age of onset for any substance is going to increase your risk for addiction, and it’s going to increase your risk for its effects…for the cannabis, we’re looking at increased risk for development of psychosis, increased risk for cognitive impairment,” Robinson Barrett said.

She also highlighted people who are genetically vulnerable, or have a family history of mental illness as well as heavy users who smoke regularly.

While cannabis has many cannabinoids, Robinson Barrett explained that the main ones are Delta-9-THC, which most people know as a psychoactive component, and CBD, which can have a calming or relaxing effect.

Kazaara agreed that cannabis misuse can complicate mental health treatment.

“Yes, it does. Cannabis complicates the treatment of psychiatric conditions. For example, in the case of schizophrenia, it can worsen symptoms and also make the medication we use for it, less effective,” he explained.

In the meantime, Atkinson stressed that the NCDA was not demonising cannabis, highlighting the medicinal benefits and scope for a medicinal industry.

“We recognise the value, but we see the downside in our clients and in some of the young people who we have to treat,” she explained.

She urged that use must be balanced with ensuring that the population, especially youth and those with a predisposition to mental illness, understand the risk of use, particularly in a problematic manner.