FRIDAY, Sept. 9 (HealthDay News) -- Almost half of all the U.S. adults who experienced physical or psychological problems in the months following the 9/11 terrorist attacks still struggle with feelings of fear and anxiety 10 years later, a new Harris Interactive/HealthDay poll found.

The most common lingering concerns are worry about family and friends, reported by 24 percent of those still affected, and anxiety, by 13 percent. Twelve percent said the disaster has caused them to "lose hope" about the future.

In addition, 19 percent of all those polled reported they now have a fear of flying. That percentage increased at least 4 points for those who were in, or had family or friends in, New York City or Washington, D.C., when the hijacked planes hit on Sept. 11, 2001.

"People are still struggling with this, and it seems to have impacted more fragile people and those more directly affected by the attacks," said Alan Hilfer, director of psychology at Maimonides Medical Center in New York City.

And, while continued stress is normal after any catastrophe, Hilfer said, "I know people who are still afraid to cross bridges and get on airplanes."

Overall, 46 percent of those who experienced any effects following the 9/11 attacks said they still had lingering effects.

But 9 percent of all the approximately 2,200 people polled admitted they feel anxious in big cities or crowded venues, 18 percent said they want revenge against terrorists, and 14 percent said they feel "nervous" when they see people dressed in traditional Muslim attire.

Two-thirds of all those polled said they had taken action as a result of 9/11: 47 percent said they now try to appreciate life more, and 34 percent reported spending more time with family and friends.

And while only 10 percent said they turn more often to their church or place of worship, 21 percent said they pray more often or more intently.

Thirty-one percent said they had family or friends near lower Manhattan or the Pentagon 10 years ago, the targeted sites of the plane attacks, while 4 percent were actually in one of those two locations.

Priscilla Dass-Brailsford, a professor of psychiatry at Georgetown University in Washington, D.C., said, "It's very normal, very natural for people to have these reactions and lingering effects."

But it's not clear what the future holds for those still suffering, she added. Hopefully, she said, the numbers will diminish with time, but current problems like the ailing economy and the destruction from Hurricane Irene may impede the healing process.

Ultimately, though, the 9/11 attacks were fundamentally different from calamities such as natural disasters, Hilfer said.

"What still lingers -- and what the legacy of Sept. 11 was -- is that we are vulnerable to terrorist attacks and they are completely out of our control," he said. "They are as a result of people who we consider to be maniacal. [Hurricane] Katrina was an act of nature and it's a different kind of anticipatory anxiety. We know we can get hit by a hurricane again. But it doesn't have the same kind of impact as being impacted by other human beings."

Regina A. Corso, senior vice president of the Harris Poll, Public Relations and Youth Research, added: "Even though it has been 10 years, the impact of 9/11 is something that was not constrained to just that one day or even to a few weeks after the attacks. Not only did more than two in five Americans experience effects such as worry or anxiety after the event, almost half of those people say they are still experiencing effects a decade later.

"But, what is nice to see," she added, "is that not all effects are negative. Almost half of Americans say they, as a result of 9/11, are trying to appreciate life more, and one-third are trying to spend more time with family, loved ones or friends."

The survey was conducted online within the United States from Aug. 25-29, among 2,202 adults aged 18 and older. Figures for age, sex, race/ethnicity, education, region and household income were weighted where necessary to bring them into line with their actual proportions in the population.

More information

Visit the World Trade Center Health Registry for more on the physical and mental health effects of 9/11.

To read HealthDay's story on the psychological toll of 9/11 on people in New York and Washington, D.C., click here.

To read HealthDay's story on how 9/11 has shaped the lives of many young Americans, click here.

To read HealthDay's story on the lasting health problems of 9/11 first responders, click here.