Study co-authors Laura Juliano of American University, Steven Meredith and Roland Griffiths of the Johns Hopkins University School of Medicine and John Hughes of the University of Vermont, said many people are dependent on caffeine to the point that they suffer withdrawal symptoms and are unable to reduce caffeine consumption even if they have another condition that may be negatively impacted by it -- such as a pregnancy, a heart condition, or a bleeding disorder.
"The negative effects of caffeine are often not recognized as such because it is a socially acceptable and widely consumed drug that is well integrated into our customs and routines," Juliano said in a statement. "And while many people can consume caffeine without harm, for some it produces negative effects, physical dependence, interferes with daily functioning, and can be difficult to give up, which are signs of problematic use."
The study, published in the Journal of Caffeine Research, found biological evidence for caffeine dependence, data that showed how widespread dependence is, and the significant physical and psychological symptoms experienced by habitual caffeine users.
However, some in the scientific community are beginning to wake up and smell the coffee, Juliano said. Last spring, the American Psychiatric Association officially recognized Caffeine Use Disorder as a health concern in need of additional research in the Diagnostic and Statistical Manual of Mental Health Disorders -- used by mental health professionals in the United States.
Based on current research, Juliano advised healthy adults to limit caffeine consumption to no more than 400 milligrams per day -- or about two to three 8-ounce cups of coffee. People who regularly experience anxiety or insomnia -- as well as those with high blood pressure, heart problems, or urinary incontinence -- should also limit caffeine, she said.
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