You say you can’t put down your smartphone? It might be smarter to do so when you’re driving, walking, or exercising. Using the phone too much can cause other problems, too.

Many of us feel we just can’t live without our smartphones and other mobile devices. But depending on where you are and what you’re doing, using your smartphone might be pretty dumb.

That’s because a growing body of research shows that using your smartphone could put you at risk. You may endanger:

• Your safety, by using a smartphone while driving or walking
• Your health, by causing wear and tear on your thumb or eyes
• Your behavior, by becoming, in effect, a smartphone addict

Dial D for Distraction
A lot of us ignore warnings—and even laws—against texting or talking on the phone while driving. Yet every day, car crashes linked to distracting cellphone use kill three Americans and hurt 66, according to the Centers for Disease Control and Prevention (CDC). (See “Driving and Smartphone Use Don’t Mix” below.)

But you can become just as distracted while crossing a street on foot. Last year, researchers at New York University Langone Medical Center analyzed the cases of more than 1,400 pedestrians who had been struck by motor vehicles and treated in a New York City emergency room. When they were hit, one in five older children and one in 10 adults were using electronic mobile devices, such as cellphones and music players.

Researchers at the University of Washington watched 1,100 pedestrians cross 20 busy Seattle intersections last summer. Their study also found that distracted walking threatens your safety. Three out of 10 pedestrians were distracted electronically: 11 percent were listening to music, 7 percent were texting, and 6 percent were talking on the phone.

Texting was the riskiest behavior. It took people who were texting almost two seconds longer than other pedestrians to cross streets. Texters were four times more likely to ignore traffic lights, cross where they shouldn’t, or fail to look before crossing.

Besides warning against texting while driving or walking, the American College of Emergency Physicians discourages texting while biking, in-line skating, or otherwise exercising. Emergency room doctors see a lot of trip-and-fall injuries caused by walking or exercising while texting and talking.

Strains on Your Body
All that texting with our thumbs has led to a disorder variously called BlackBerry thumb, iPhoneitis, and texting thumb. These new names describe what is essentially thumb tendinitis. Constant texters with achy hands and wrists have also been diagnosed with carpal tunnel syndrome.

The American Physical Therapy Association suggests ways to limit problems:

• Take frequent breaks from typing on your smartphone.
• Write fewer and shorter messages.
• Use your fingers to type instead of just your thumbs.

Your eyes may suffer, too. When browsing the Web or texting on a smartphone, people tend to hold the devices closer than a book or a newspaper because the screens, and in some cases the letters, are so small. Researchers in the journal Optometry and Vision Science found that the extra demands on your eyes could eventually cause problems. After prolonged use, you could suffer eyestrain, headaches, eye discomfort, dry eye, double vision, and blurred vision.

Behavioral Effects
The American Psychiatric Association already acknowledges that “Internetuse gaming disorder” could be classified as an illness after more study.

Now there’s something called “nomophobia,” short for “no-mobilephone phobia.” Nomophobia is defined as the fear of losing or being without your mobile phone. The Morningside Recovery Center, a California drug and alcohol treatment facility, recently started what is billed as the nation’s first nomophobia recovery group.

How much do we rely on our smartphones? Harris Interactive last year conducted an online survey of nearly 2,100 adults for Lookout Mobile Security. The findings:

• 58 percent of smartphone users overall—and 68 percent of 18- to 34-year-olds—check their smartphones more than once an hour
• 73 percent panic when they can’t find their smartphones
• 54 percent check their phones in bed, 39 percent in the bathroom, 30 percent while dining with others, and 9 percent during religious services

Researchers who studied 163 U.S. and Finnish smartphone users concluded the devices really are habit-forming. The researchers identified people’s habits for checking their smartphones. A typical check lasted less than 30 seconds, but the number of daily checks averaged 34. The researchers concluded that what we often call Internet or media addiction is better described as “overuse due to loss of self-control.”

Grammar Risks
Finally, texting may not just harm people’s health—it may harm their language.

An adolescent between ages 13 and 17 sends an average of 3,339 text messages a month. Many abbreviate and shorten words while ignoring punctuation and capitalization rules. A study last year in New Media & Society concluded that the more middle-school children send text messages and communicate in such tech speak, the worse they did in grammar assessments.

Are concerns such as these likely to make you toss out your smartphone? Probably not. But it may help to be aware of potential safety issues. With that knowledge, you can exercise caution and good judgment in using all your mobile devices.

By Bruce E. Beans, a feature writer for Vitality. To learn more, visit www.distraction.gov.