Addiction. 2021 Feb 23. doi: 10.1111/add.15447. Online ahead of print.
BACKGROUND/AIMS: Research linking orbitofrontal cortex (OFC) structure and substance use disorders (SUDs) is largely correlational and often implies a causal effect of addiction/substance exposure on the brain, but familial risk factors (e.g., genetic liability) may confound these associations. We tested whether associations between alcohol, cannabis, and tobacco use disorders and OFC thickness reflected the potential causal effects of familial risk or SUDs-related consequences (e.g., substance exposure).
DESIGN: A cotwin control/discordant twin design separated familial risk confounding from SUDs-related consequences.
SETTING/PARTICIPANTS: A population-based sample of 436 24-year-old twins (62% monozygotic) from the Minnesota Twin Family Study, USA.
MEASUREMENTS: Alcohol, cannabis, and tobacco use disorders were assessed using the Composite International Diagnostic Interview – Substance Abuse Module. Cortical thickness of the medial and lateral OFC (mOFC and lOFC, respectively) was assessed using MRI.
FINDINGS: Lower mOFC (p-values ≤0.006) but not lOFC (p-values ≥0.190) thickness was observed in diagnosed individuals (n = 185) relative to non-SUDs controls (n = 251). Cotwin control analyses offered evidence that mOFC associations were consistent with familial risk across SUDs (between-pair effect: p-values ≤0.047) and the independent consequences of having an alcohol or cannabis use disorder (within-pair effect: p-values ≤0.024). That is, within alcohol/cannabis discordant twin pairs, affected twins had significantly lower mOFC thickness compared with their unaffected cotwins.
CONCLUSIONS: A confounder adjusted analysis of the Minnesota Twin Family Study appeared to indicate that, beyond a substance use disorders general familial risk effect, the experience of an alcohol or cannabis use disorder in emerging adulthood reduces the thickness of the medial orbitofrontal cortex, a region associated with value-guided decision making.
Source: ncbi 2