None of the women had a current alcohol-use diagnosis, and none had been treated for alcohol problems.
"Results of this study suggest that genetic vulnerability reflected in a family history of alcoholism may also be at the root of the inability to stop caffeine use," said co-lead author Roland R. Griffiths, Ph.D., a professor in the departments of Psychiatry and Neuroscience at The Johns Hopkins University School of Medicine.
The study appears in the December issue of the American Journal of Psychiatry.
Griffiths, whose past studies of caffeine use helped establish the drug's addictive nature, collected data on caffeine and alcohol use from 44 pregnant women seeking prenatal care from a private obstetrics and gynecology practice in a suburban community. Results showed that half of the women who had both a lifetime history of caffeine dependence and a family history of alcoholism ignored their doctor's recommendation to abstain from caffeine use and consumed caffeine in amounts greater than those considered safe during pregnancy.
Women in the study without these dual risk factors were able to abstain from caffeine during pregnancy, Griffiths said.
"This study helps to validate the diagnosis of caffeine dependence as a clinically significant phenomenon," Griffiths said. "It's one thing to speculate how powerful the dependence is, but here we have an example of people who are not following physician recommendations and are unable to quit caffeine in spite of wanting to do so."