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Orbitofrontal cortex thickness and substance use disorders in emerging adulthood: causal inferences from a co‐twin control/discordant twin study
Author(s) -
Harper Jeremy,
Wilson Sylia,
Malone Stephen M.,
Hunt Ruskin H.,
Thomas Kathleen M.,
Iacono William G.
Publication year - 2021
Publication title -
addiction
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.424
H-Index - 193
eISSN - 1360-0443
pISSN - 0965-2140
DOI - 10.1111/add.15447
Subject(s) - cannabis , orbitofrontal cortex , twin study , monozygotic twin , confounding , addiction , medicine , alcohol use disorder , substance abuse , psychiatry , psychology , clinical psychology , alcohol , cognition , prefrontal cortex , genetics , heritability , biochemistry , chemistry , biology
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 co‐twin control/discordant twin design separated familial risk confounding from SUD‐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 magnetic resonance imaging (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‐SUD controls ( n = 251). Co‐twin 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 co‐twins. 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.