More Americans take prescription medications than ever before – nearly 60% – and obesity could be to blame.
A new study published in JAMA shows that the number of people taking prescription drugs increased from 51% of the adult population in 1999 to 59% in 2011. Cholesterol and blood pressure drugs are the most-used medications in the U.S. 
Additionally, the number of people taking 5 or more prescriptions in a month has doubled to nearly 15%. 
“When we’re starting to see more and more adults using five or more drugs, it does raise a concern about the potential for drug interaction,” says Elizabeth Kantor, who is now an epidemiologist at Memorial Sloan Kettering Cancer Center in New York and the lead researcher on the study.
Kantor explains that while the U.S. population is aging, that alone doesn’t account for the jump. Obesity has become a health crisis in America, so in addition to getting older, many people are suffering obesity-related diseases like heart disease, diabetes and other metabolic disorders. 
“This might raise the question of how much of this increase in prescription drug use might be attributable to obesity, as we know that the prevalence of obesity has increased among adults in the United States,” she says.
For the study, Kantor and her colleagues analyzed data from the National Health and Nutrition Examination Survey to compare prescription drug use from 1999-2000 and from 2011-2012. People participated in the survey by answering questions in their homes about which prescription drugs they had used in the previous 30 days. Interviewers asked the participants to show them their prescription medication containers. The survey spanned 2 years and included 40,000 individuals.
The researchers discovered that 8 of the 10 most commonly used drugs in the U.S. are used to treat high blood pressure, heart failure, diabetes or other aspects of “cardiometabolic syndrome.” Specifically, statins increased from 6.9% to 17%, and antidiabetic drugs increased from 4.6% to 8.2%.
Another of the most commonly prescribed drugs is used to treat gastroesophageal reflux (GERD), which is also associated with being overweight or obese.
GERD is a condition caused by stomach acids and other stomach contents backing up into the esophagus through the lower esophageal sphincter, which is usually either damaged or weakened, often by excess weight. The condition causes heartburn, a sour taste and regurgitation. Rarely, the condition can make people vomit. There are numerous ways of treating GERD naturally, without medication. 
In addition to getting wider, the survey found that Americans’ mental health is declining, which may also be linked to obesity. Antidepressants increased from 6.8% 13%, and tranquilizers and sedatives increased from 4.2% to 6.1%.
The only type of prescription drug use that decreased was sex hormones for women (declining from 19% to 11%) and antibiotics (from 5.7% to 4.2%). Studies have shown that women who take estrogen to treat the symptoms of menopause have a greater risk of breast cancer and other diseases, which has led to a decline in women using hormone replacement therapy.
The decrease in antibiotic use is a positive thing, though antibiotics are still widely over-prescribed, leading to a rise in drug-resistant bacteria and superbugs. 
 NBC News