Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:

Large Rise in ER Visits Linked to Illicit Use of CNS Stimulants: Report

The number of young adults treated at U.S. emergency departments for the illicit use of drugs called central nervous system stimulants rose 300 percent between 2005 and 2011, from about 5,600 to nearly 23,000, a U.S. government study released Thursday reports.

About 30 percent of those visits by adults ages 18 to 34 also involved alcohol, according to the Substance Abuse and Mental Health Services Administration.

The CNS stimulants in the study included: prescription drugs, such as those used to treat attention deficit/hyperactivity disorder; other prescription medications, such as benzphetamine and modafinil; and over-the-counter products containing stimulants. Illegal stimulant drugs like methamphetamine were not included in the study.

Illicit use of CNS prescription drugs can cause heart and blood vessel problems, and lead to drug abuse or dependence. When used with alcohol, CNS stimulants can affect a person's perception of intoxication and increase their risk of alcohol poisoning or alcohol-related injuries, SAMHSA said.

In 2011, there were a total of 1.24 million emergency department visits related to the illicit use of prescription and over-the-counter drugs, as well as supplements, according to the report.

"Nonmedical use of any drug, even an over-the-counter drug, can be dangerous, but these CNS stimulants can potentially cause significant and lasting harm, including heart problems and addiction," SAMHSA Chief Medical Officer Dr. Elinore McCance-Katz said in an government news release. "We must raise awareness of this public health risk and do everything possible to prevent it."

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Smokers More Costly for Employers: Study

A smoker costs a private employer $5,816 more per year than a nonsmoker, according to a new study.

Ohio State University researchers analyzed data from previous studies and found that $3,077 of that extra cost was due to smoking breaks and $2,056 was associated with added health care expenses, The New York Timesreported.

The remainder of the extra cost was caused by increased absenteeism and lost productivity. Smokers miss about two-and-a-half more work days per year than nonsmokers and may be less productive at work due to the effects of nicotine withdrawal, according to the study published online recently in the journal Tobacco Control.

"We certainly encourage businesses to provide smoking cessation programs. At least for large companies, it's highly likely to save them money over time," said study lead author Micah Berman, an assistant professor of public health and law at Ohio State, The Timesreported.

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Scientists Plan H7N9 Lab Tests to Learn More About Virus

Scientists plan to make more dangerous versions of the H7N9 bird flu virus in the lab, to learn more about how likely it is that the virus will mutate and cause a human pandemic, and how to protect people against it.

The project is outlined Wednesday in the journals Scienceand Nature.

The researchers will conduct gain-of-function experiments on H7N9. These types of experiments introduce changes into a virus to learn more about it. For example, such tests can show whether certain mutations would increase the ability of the virus to spread or would affect how the virus responds to vaccines, according to a Sciencenews release.

A related letter also published in both journals provides the U.S. Department of Health and Human Services' official statement about the oversight it will require for this research.

The bird flu virus first emerged in China in February. By the end of June, 133 cases had been reported, resulting in 43 deaths.