cannTEEN: a longitudinal, MRI study investigating how cannabis differentially affects teenagers and adults

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Dr Will Lawn

Research Associate

Will is a post-doctoral researcher at University College London’s Clinical Psychopharmacology Unit. He works on the cannTEEN project, which is investigating if and how cannabis differentially affects teenagers and adults. Previously, Will worked as a post-doc on the KARE clinical trial, which examined ketamine as a treatment for alcohol dependence. Will received his PhD from UCL on the topic of reward processing in cigarette and cannabis users and his Bachelor’s degree from the University of Cambridge in Experimental Psychology.



Adolescence is a period in which the brain and mind continue to develop, and it is thought that the harms associated with cannabis may be greater during adolescence than in later years. Despite these concerns, studies directly comparing teenage and adult cannabis users are scarce.

I will describe a new longitudinal, magnetic resonance imaging (MRI) study of four groups, made up of teenagers (16-17 years) and adults (26-29 years) who do and don’t smoke cannabis (aim total n=272). The study is currently in progress (current n=183, March 2019). Participants attend five behavioural sessions over one year (one session every three months), when we measure cannabis addiction, mental health, cognitive functions and endo- and exogenous cannabinoid levels. A subsection of participants (n=140) attend an MRI session at the start and end of the year, when we record blood oxygen level dependent (BOLD) response associated with reward anticipation, working memory and response inhibition, alongside brain structure and white matter integrity.

The overall aim of the project is to determine whether teenage cannabis users show more adverse changes than adult cannabis users (in comparison to their non-using control groups) in mental health, cognitive and neural domains over one year.

By autumn 2019 we will have collected our baseline data for the whole sample. I will report initial, cross-sectional differences between our four groups on cannabis addiction, psychotic-like symptoms, and BOLD response associated with reward anticipation and response inhibition.

This research is funded by the Medical Research Council.