It is considered that cocaine could be a risk factor for the development of alcohol dependence. Prospective studies in healthy subjects support the idea that alcohol and cocaine use decreases the subjective feeling of inebriation and increases the sense of being “high”. The consumption of both drugs may accentuate the reinforcing properties of both drugs, thus increasing the vulnerability of subjects for developing drug dependence. Our objective was to investigate whether the risk for the development alcohol dependence is related with the interaction of both drugs at reward brain mesolimbic centres or it depends on the effect of cocaine at that brain mesolimbic structures.

The final sample (n = 112) comprised 4 groups: sample 1(alcohol-group), n = 47; sample 2 (alcohol-cocaine group), n = 35; sample 3 (cocaine-group), n = 30. The control group (n = 61) was selected to have matching demographic characteristics. After detoxification, alcohol-related pictures were compared to standardised appetitive, aversive and neutral control scenes using an acoustic-startle test.

Alcohol-startle magnitudes were lower in cocaine-dependent patients (samples 2 and 3) than in alcohol patients (sample 1). Subjects with cocaine dependence also exhibited lower magnitudes than participants included in the OH-group after viewing appetitive and aversive slides.

Our findings support the hypothesis that effects of cocaine at dopamine mesolimbic structures provoke higher appetitive responses to alcohol-cues. It is tempting to speculate that cocaine use may induce significant reduction in dopamine D2 receptors, which would increase the likelihood of developing dependence for other substances as alcohol used at the same time than cocaine.