If someone you love has been diagnosed with cancer, you want to see him do everything he can to stay healthy and safe. So it can be confusing or upsetting if he does things that seem risky. But experts say unexpected behavior is a normal part of the way some people handle their diagnosis.

“Facing a life-threatening illness can shift your perspective, both in the short- and long-term,” says Jeremy Winell, MD. He's the director of cancer supportive services at Mount Sinai Beth Israel Cancer Center in New York City. “Some changes in behavior and attitude are to be expected.”

One Person’s Risk Is Another Person’s Bucket List

Research shows that cancer survivors are more likely to make positive health changes than negative ones. But if your loved one is doing something that concerns you, try to put his behavior into perspective -- and learn when to take action.

Truly risky behavior -- like having unprotected sex, or driving 90 miles an hour -- is a rare reaction to cancer.

“In 30 years of practice, I can’t recall a time that a patient did something dangerous in response to their diagnosis,” says Stewart Fleishman, MD. He's a psychiatrist, palliative care specialist, and author of Learn to Live Through Cancer.

More often, experts say, a cancer diagnosis reminds people how short life is. They may feel the need to do things they always wanted to do but had been putting off, like driving a race car or going sky diving. Many survivors decide to change careers, and some even choose to endrelationships with their significant others.

Should you worry? Winell says most of the time, there’s no need.

“Their loved ones may get concerned, and feel like the patient’s having a personality change, when in fact they’re doing something normal and not necessarily unhealthy,” he says. 

Addictive Behaviors Are Hard to Shake

Some people will turn to unhealthy ways to deal with their diagnosis, though, especially if that’s how they tend to handle anxiety. Cancer can be extremely stressful, after all.

“That’s why it can be hard to give up so-called risky behaviors that people use to cope with stress, like smoking, drinking too much alcohol, doing drugs, or even overeating in the middle of treatment,” says Diane Robinson, PhD. She’s a neuropsychologist and director of the cancer support community at the University of Florida Health Cancer Center-Orlando Health.

A person’s struggles with substance abuse can get even worse if he’s stressed out. That may be why a recent American Cancer Society study shows that about 1 in 10 cancer survivors continues to smoke.

“If you’ve never been a smoker, it may seem shocking that someone wouldn’t do everything they can to reduce their risk of getting cancer again,” says study author Lee Westmaas, PhD. He's the director of Tobacco Control Research at the American Cancer Society. “But nicotine is incredibly addictive and actually changes brain chemistry in ways that can make it difficult to quit.”

Many people living with cancer find healthy ways to ease stress, though. If your loved one hasn’t yet, gently encourage him to talk to his doctor. Smokers can get free, cancer-oriented support at SmokeFree.gov and 800 Quit-Now.