U.S. researchers said popular antidepressant Lexapro showed results of being "modestly beneficial" in easing anxiety symptoms in very anxious older adults though further studies were called for.

In the study researchers studied one specific drug, Lexapro, made by Forest Laboratories Inc (FRX.N) and known generically as escitalopram which is part of a class known as selective serotonin reuptake inhibitors (SSRIs), to see if it could relieve symptoms of generalized anxiety disorder (GAD) in older adults. GAD is a disabling condition which apart from anxiety can cause muscle tension, insomnia and fatigue. Sufferers of this condition worry chronically and can't seem to stop, with their quality of life affected and nearly one in 10 older adults is affected by GAD.

The SSRI’s are prescribed for both anxiety and depression and are believed to work by correcting the imbalance of serotonin, a brain chemical. Study researcher Dr. Eric J. Lenze, MD, associate professor of psychiatry at Washington School of Medicine in St. Louis said, "Although these medications have been examined in younger adults, there has been very little examination of them in older adults."

In the study Lenze and his colleagues gave 85 adults with GAD and an average age of 71, Lexapro and 92 adults with GAD and average age of 72, placebo pills for 12 weeks. During this period Lenze's team measured the participants' anxiety and other factors, such as social functioning and limitations in activity due to anxiety.

The team reported that at the end of 12 weeks, 69 % of the medication group had a favorable response and showed more improvement in anxiety symptoms and their functioning as compared to 51 % in the placebo group. "We found improvements not only in anxiety and level of worry but also in functioning," said Dr. Lenze.

However when the researchers calculated the participants who had dropped out of the study they found the response was 57 % for those who were on the medication versus 45 % who were on a placebo which was not a significant difference.

"A short conclusion is that the drug was modestly beneficial, and even those modest benefits can only be seen if someone sticks with the medication long enough to see if it will help or not," Lenze said. The drug he said took about four weeks to start showing any benefits. "In older people the drugs may take longer to work," Lenze added. "Patients need to be aware of that. They shouldn't expect immediate benefits."

"The data doesn't come as a surprise," said Philip Muskin, MD, a professor of clinical psychiatry at Columbia University College of Physicians and Surgeons and a psychiatrist in New York City. "Those who stayed on the drug and took it got better, and more [of them] got better than the placebo group.”

He added that "No one had really bad side effects" from the drug, with fatigue or sleepiness being the most common side effects.

Another unexpected benefit Lenze's team found was that the drug helped people get their blood pressure under control. "That suggests there can be some long-term health benefits in treating anxiety in this older age group," Lenze said.

"Overall the benefits were fairly modest," Lenze said. "It will help some people a lot. Most people will probably need some sort of combination treatment."

The study was funded by a variety of sources, such as the National Institutes of Health and Forest Laboratories Inc., which makes Lexapro, provided both the drug and placebo but had no role in the study. The results are published in The Journal of the American Medical Association.  (Additional Reporting by Harkiran)