Gianoulakis said that a specific response may depend on the dose of alcohol as well as the species involved. "For example, in experimental animals such as rats, all doses of alcohol increase the release of β-endorphin," she said. "However, in humans low doses of alcohol have either no or a small effect on β-endorphin release, whereas high doses of alcohol are needed to induce a significant increase in β-endorphin release."
For this study, four groups of individuals participated: social and heavy drinkers with a family history of alcoholism (considered "high risk") and without a family history of alcoholism (considered "low risk"). Each participant was given either a placebo or alcohol (0.50g ethanol/kg) drink; researchers then measured their responses to both drinks as well as a stress test performed 30 minutes following ingestion. The stress test had two components: arithmetic computations, and a competition for monetary reward. Plasma β-endorphin levels were also measured prior to and for 3.5 hours after the stress test.
Results indicate that there are differences in both the basal plasma β-endorphin levels as well as the response of the pituitary β-endorphin to stress as a function of an individual's family history of alcohol problems.
"There are two major findings in this study," said Gianoulakis. "In participants with a family history of alcoholism, the lower activity of the pituitary β-endorphin system indicated by the low basal plasma β-endorphin levels and the lower β-endorphin response to stress predate the development of alcoholism, and alcohol dependence does not induce a further decrease in the activity of the pituitary β-endorphin system.