Does thinner right entorhinal cortex underlie genetic liability to cannabis use?

Area of Science:

• Neuroscience
• Genetics
• Psychiatry

Background:

• Cannabis is a widely used illicit drug.
• Previous studies suggest a link between cannabis use and medial temporal lobe alterations.
• The causal relationship between cannabis use and these brain changes remains unclear.

Purpose of the Study:

• To investigate the association between cannabis use and cortical thickness and surface area.
• To explore the genetic and environmental contributions to cannabis use and brain morphology.
• To determine if cannabis use causes alterations in medial temporal lobe structures.

Main Methods:

• Cross-sectional observational study of 404 twins/siblings.
• Comparison of cortical thickness and surface area in gender-matched sibling pairs (concordant/discordant for cannabis exposure).
• Permutation tests and bi-variate polygenic models were used to control for confounds and assess genetic/environmental contributions.

Main Results:

• Significantly lower cortical thickness in the right entorhinal cortex was observed in cannabis-exposed siblings.
• This association is partly explained by shared additive genetic factors.
• Preliminary evidence suggests a causal effect of cannabis use on right entorhinal cortex surface area, though polygenic models showed no significant effect.

Conclusions:

• Shared genetic liability may explain the link between cannabis exposure and reduced entorhinal cortex thickness.
• Prospective longitudinal studies are required to establish a definitive cause-effect relationship between cannabis use and brain alterations.