New research into the effects of cannabis use

New research into the effects of cannabis use
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The health effects of cannabis use have now been addressed in a new doctoral thesis from the Karolinska Institutet in Sweden.

Over 200 million people around the world use cannabis, a substance that implicates brain function, human behaviour and consciousness. The current understanding of the effects of cannabis on mental health is inconclusive. There are some associations that psychotic disorders can be a result of cannabis use; however, more research is needed.

“More knowledge about the health effects of cannabis use is needed for well-informed decisions to be made by medical and public health professionals,” said Rynaz Rabiee, a doctoral student at Karolinska Institutet’s Department of Global Public Health. “My results emphasise individuals with complex care needs and stress the significance of comorbidity in psychiatric care.”

The health effects of cannabis

In the thesis, Rabiee studied the link between the use of cannabis and other illicit drugs and subsequent drug use disorders amongst more than 9,700 adults over 16 years. The results showed that cannabis use was not an independent risk factor for drug use disorders.

“The association between cannabis use and subsequent drug use disorders rather seems to be explained by other drug use,” she said. “Cannabis use was linked to an increased risk of other drug use at the three-year follow-up.”

The risk of other drug use was highest amongst those who had used cannabis in the past year, almost ten times higher than those who never used drugs.

She also examined the connection between the effects of cannabis use on anxiety and depression prevalence over time in 1,100 women born between 1955 and 1993.

“Since cannabis has increased in potency over the past 20 years, we wanted to see if the association was stronger among the women who had used cannabis during this time,” she explained. “We saw that the youngest women who had used cannabis had over two times higher risk of being diagnosed with depression than those who did not use cannabis. This association was more pronounced when we added the effect of when these women used cannabis.”

Analysing cannabis-related diagnosis

Furthermore, Rabiee looked closely at individuals who had received a cannabis-related diagnosis and the effects of cannabis on these individuals in Sweden using data from the National Patient Register for over 3.3 million people born between 1970 and 2000.

The results indicate that cannabis-related diagnoses have gradually risen in Sweden and that younger people are driving the increase. In 2006, six per 100,000 born between 1990 and 1994 had such a diagnosis, compared to 61 per 100 000 in 2016. An increase was also seen among those born from 1995 to 2000, from nine per 100,000 in 2010 to 107 per 100,000 in 2016.

The research found that men from younger age groups with a lower level of education and income than those without a diagnosis. A majority also had an additional psychiatric diagnosis.

The thesis looked at factors that could include the risk of readmission to cannabis-related care.

“We noted that over one-fifth of the patients returned to cannabis-related care during the 15-year follow-up period and that people with low education, psychotic disorders, mood-related disorders, or personality disorders had the highest risk of readmission. Younger individuals, those between 18 and 35, also had a higher risk,” noted Rabiee.


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