The impact of high and low potency cannabis on paranoid symptoms in a general adolescent population sample

Background: Cannabis use remains the most used illicit drug among adolescents in Europe. The number of adolescents entering specialist drug treatment for cannabis problems has risen considerably in recent years. On reason for this increase is that cannabis is becoming increasingly potent and has been linked to poor mental health and cannabis dependence.

Aims: To identify the frequency and quantity of cannabis products used by adolescents in the UK and to examine the association between high and low potency cannabis to psychotic symptoms.

Design: Cross-sectional study

Setting and participants: Data was collected from 467 14-15-year adolescents aged between 14-16 years attending seven secondary schools in Greater London randomly sampled to reflect diversity in socio-economic status, ethnicity and gender forming a representative adolescent population sample.

Measurements: Five types of psychotic experiences were assessed: paranoia, hallucinations, cognitive disorganisation, grandiosity, anhedonia via self-report. Cannabis type was classified into ‘high potency’ (i.e. skunk), ‘low-potency’ (i.e. herbal or grass) and resin. Participants were asked to report on frequency, amount of cannabis (number of joints and grams), accessibility and preference.

Findings: 30.4% of adolescents reported using cannabis in the previous 6 months. Low-potency cannabis was used by 75.4% (n=107) of cannabis using adolescents. 50.7% (n=72) reported high-potency cannabis use and 12% (n=17) reported using cannabis resin. Controlling for demographics, alcohol, other illicit drug use, depression and anxiety, adolescents who reporting using high-potency cannabis at least twice a month or more were 1.7 times more likely to report paranoid symptoms than non cannabis users (95% CI = 1.1-2.7). Adolescents who reported smoking at least 2 or more joints on one occasion of high potency cannabis were 1.8 times (95% CI = 1.3-2.7) more likely to report paranoid symptoms than non cannabis users. Reverse associations were also examined and adolescents who reported more severe paranoid symptoms were 4.9 time more likely (95% CI 2.1-11.1) to use low potency cannabis at least twice a month than non cannabis users. No association was demonstrated between cannabis use and any other measure of psychotic experience.

Conclusions: Different pathways to paranoid symptoms exist for adolescents who report preferences for high and low cannabis potency products. Adolescents using cannabis products high in THC frequently and in large amounts are at an increased risk of experiencing symptoms of paranoia. Of interest is the association between rare or severe paranoid symptoms and the frequent use of low potency cannabis. This would suggest that adolescents with a predisposition to develop psychotic like experiences are more likely to use cannabis to manage their symptoms. Prevention programs would need to address these different pathways to comorbid substance use and mental health problems in young people.