Combined effects of nicotine and alcohol on subjective, behavioral and physiological responses in humans

Nicotine and alcohol have each been widely studied in humans, but there has been relatively little attention paid to their combined effects. This is surprising, given the high frequency with which they are consumed together. The limited literature on these combined effects is murky, partly because of failure to recognize that alcohol can have contrasting subjective mood effects depending on whether blood alcohol level is ascending or descending. However, in general, nicotine and alcohol (when blood alcohol level is descending) tend to have contrasting effects on mood ("stimulating" vs. "sedating", respectively), behavioral performance (slightly improving vs. impairing, respectively), and selected physiological responses (e.g. increased beta EEG vs. increased α EEG, respectively), but similar effects on other physiological responses (e.g. heart rate). Thus, when consumed together, mood, performance, and EEG responses are often intermediate between those due to alcohol alone or nicotine alone. Responses influenced in the same direction by either, such as cardiovascular effects, are exacerbated beyond effects due to either alone. Since mood and behavioral effects are likely to reinforce drug use, the attenuating influence of nicotine on alcohol's sedative effects could explain the frequently observed increase in smoking after alcohol consumption. At the same time, nicotine plus alcohol may exacerbate some physiological responses (e.g. cardiovascular) that can impact negatively on health. Limitations of this research and possible mechanisms of interaction between nicotine and alcohol are briefly noted. The need to consider the modulating influences of environmental and baseline-relevant factors is also emphasized.