A study published in the journal Alcohol investigated the biological effects of alcohol and stress on mice.
In the United States, 25% of people die from the overconsumption of alcohol. With stress, casual drinking may become excessive and this can propel the shift from binge drinking to alcohol dependence.
Alcohol dependence is often seen among individuals with posttraumatic stress disorder where their stress leads them to drink, and the drinking, in turn, exacerbates their stress disorder. It is known that the area of the brain involved in stress responses is also impaired in those with alcohol dependence.
To help explain the biological changes in the brain and to better understand the relationship between alcohol and stress, researchers studied the behaviours and blood of mice prior to and after binge drinking. They published their results in the journal Alcohol.
For the intervention, mice in the binge drinking groups received ethanol every three days for a total of seven sessions. On non-session days they were given water. After the intervention, mice received food and water, but no alcohol for one month. Mice in the control group only received water for the duration of the study.
Following the alcohol-free month, researchers regularly introduced a stressor, dirty rat nestlings, and measured mice alcohol and water intake for a month. Researchers also measured stress by measuring corticosterone levels in their blood and anxious behaviour.
To measure anxious behaviour they used an elevated plus maze in which anxious mice spend more time in closed off areas when anxious, and spend more time in open areas when not anxious. The mice were subsequently euthanized, and their brains were tested to measure protein levels. To stimulate stress, the researchers placed dirty bedding in the mice cages and measured blood corticosterone levels.
Male mice with prior binge drinking experience increase alcohol intake following stress
Binge-drinking male mice increased their alcohol intake following exposure to stress, but this effect was not seen in female mice. Although female mice did increase their alcohol intake after stress, both the control group and binge drinking group increased their intakes similarly. It is important to note that there were no significant differences in body weight between male and female mice.
Interestingly, although mice who consumed alcohol experienced an increase of corticosterone upon exposure to stress, these mice had lower corticosterone levels than those who only drank water, suggesting alcohol may interfere with stress responses.
Alcohol consumption with stress may result in more alcohol intake
In summary, the study shows that together, alcohol and stress can result in even more alcohol intake. Furthermore, the effects differ between males and females. Males seemingly have a higher alcohol tolerance, but as all mice had similar body weights, chemical differences between the two must exist. This is important when dealing with individuals with posttraumatic stress disorder as treatments will likely differ between the two sexes.
Written by Monica Naatey-Ahumah, BSc
Reference: Deborah A. Finn, D.A., Helms, M.L., Nipper, M.A., Cohen, A., Jensen, J.P., and Devaud, L.L. (2018). Sex differences in the synergistic effect of prior binge drinking and traumatic stress on subsequent ethanol intake and neurochemical responses in adult C57BL/6J mice. Alcohol, 71, 33-45. https://doi.org/10.1016/j.alcohol.2018.02.004
