How does cannabis use affect teenagers' brains, cognitive functions and psychological well-being? (CANN-TEEN)

点击翻译按钮获取中文摘要

How does cannabis use affect the teenage brain, cognitive function and psychological well-being? This is an important question for several reasons. 1. Across the globe, more people use cannabis than any other illicit drug and roughly half of them start using it before they are 18 years of age. 2. The active ingredient in cannabis - THC - causes more profound and persistent harms to adolescent rats and monkeys than it does in adult animals. 3. The brain's 'own cannabis' system - the endocannabinoid system - is critically important to brain development in adolescence and can be disrupted by cannabis use. 4. The strength of cannabis has increased dramatically over recent years so very high potency varieties (15% THC or more) are what most teenagers get when they start using. 5. The high potency varieties contain virtually no cannabidiol (CBD) - an ingredient in cannabis which can protect adults against some of the harms caused by THC. 6. Across Europe, the proportion of people who become addicted to the drug is six times higher in 14-17 year olds than in adults and younger use is associated with greater risk of developing a psychotic disorder like schizophrenia. 7. Earlier cannabis use is also associated with greater risk of cognitive impairment and poorer achievement at school so can seriously affect an individual's life trajectory. We recently completed the first ever study to directly compare the effects of a single dose of cannabis in human adolescents (16-17 year old boys) with adults. Compared with adults, the teenagers showed greater impulsiveness and wanted more of the drug even when they had consumed cannabis rather than placebo. Whilst the adults showed increases in anxiety the teenagers did not, and the teenagers experienced significantly fewer negative effects including reduced physiological response and psychotic-like symptoms than adults. The teenagers' 'stop' mechanism therefore appeared switched to a 'go' profile: once they were 'stoned' they were more impulsive and wanted more cannabis. The teenagers' different pattern of response to acute cannabis could be a key mechanism mediating their increased risk compared with adults of transitioning to addiction or other mental health problems, and experiencing difficulties in cognitive functioning and educational achievement. We now need to find out how the use of cannabis affects human adolescents compared with adults over an extended period of time whilst using objective measures of cannabis (THC and CBD), alcohol, tobacco and other drug use, monitoring changes in the markers of the endocannabinoid system. This project will do this in 3 related studies. Study 1 will determine how cannabis use over a 12 month period affects psychological well-being, cognitive function and markers of endocannabinoids in 16-17 year olds compared with 26-27 year old adults. Study 2 will determine the extent to which there are differential changes in markers of brain structure and function in teenage and adult cannabis users over this same 12 month period. Study 3 is the first experiment to examine the causal effects of cannabis on the adolescent brain. It will build on the discovery in adults of the protective effects of CBD, to determine whether teenagers and adults respond differently to the acute effects of cannabis and whether this varies depending on whether the cannabis contains CBD or not. Although virtually all cannabis users experience at least transient cognitive impairments, only around 9% of adults become addicted and a smaller minority ever develops psychosis. We will also analyse our data to address this question: what factors predict vulnerability/resilience to the negative consequences of use and do these differ in teenagers and adults? Crucially, this project will enhance our theoretical and clinical understanding and provide vital information to young cannabis users, to their families, friends and those professionals who interact with them.