The Negative Effects of THC on Brain Development and Learning

A new study from the University of Montreal has revealed concerning effects of cannabis use on the developing brains of adolescents. Published in JNeurosci, the findings showed that THC, the active compound in cannabis, can cause thinning of the cerebral cortex, potentially impacting learning, memory, and emotional regulation during a critical stage of brain maturation.

“If we take the analogy of the brain as a computer, the neurons would be the central processor, receiving all information via the synapses through the dendritic network,” explained Tomas Paus, MD, PhD a lead author and professor of psychiatry and neuroscience at Université de Montréal. “So, a decrease in the data input to the central processor by dendrites makes it harder for the brain to learn new things, interact with people, cope with new situations, etc. In other words, it makes the brain more vulnerable to everything that can happen in a young person’s life.”

The researchers emphasized that THC's effects on the brain are not merely speculative but are backed by a combination of human imaging studies and experimental data from animal models. Magnetic resonance imaging (MRI) scans of teenagers showed a thinner cerebral cortex in cannabis users under the age of 16. While MRI alone couldn't establish causality, using a mouse model, the research demonstrated that THC directly impacts the genes responsible for dendritic structure and function, resulting in brain atrophy.

By integrating these findings across multiple methods, researchers said the findings provide compelling evidence that cannabis use in adolescence can contribute to cortical thinning, with long-term consequences on cognitive and emotional health. “The model made it possible to demonstrate that THC modifies the expression of certain genes affecting the structure and function of synapses and dendrites,” said lead researcher, Graciela Pineyro, PhD, of the University of Montreal.

As cannabis products become more potent and accessible, the researchers concluded that it’s increasingly important to understand how they may interfere with brain development. For integrative practitioners, the study underscores the importance of educating young patients and families about the potential neurodevelopmental risks of cannabis use.