Psychopharmacology of Tobacco and Alcohol Comorbidity: A Review of Current Evidence

Purpose of the Review Comorbidity of alcohol and tobacco
use is highly prevalent and may exacerbate the health effects
of either substance alone. However, the mechanisms underlying
this comorbidity are not well understood. This review will
examine the evidence for shared neurobiological mechanisms
of alcohol and nicotine comorbidity and experimental studies
of the behavioural consequences of these interactions.
Recent Findings Studies examining the shared neurobiology of
alcohol and nicotine have identified twomainmechanisms of comorbidity:
(1) cross-reinforcement via the mesolimbic dopamine
pathway and (2) cross-tolerance via shared genetic and nAChR
interaction. Animal and human psychopharmacological studies
demonstrate support for these two mechanisms of comorbidity.
Summary Human behavioural studies indicate that (1) alcohol
and tobacco potentiate each other’s rewarding effects and (2)
nicotinereduces the sedativeandintoxicationeffects of alcohol.
Together, these findings provide a strong evidence base to support
the role of the cross-reinforcement and cross-tolerance as
mechanismsunderlyingthecomorbidityof alcoholandtobacco
use. Methodological concerns in the literature and recommendations
for future studies are discussed alongside implications
for treatment of comorbid alcohol and tobacco use.