When Peter Carvalho quit smoking last year, it meant giving up both tobacco cigarettes and marijuana.

The latter was easy, the 27-year-old Hibbing man said.

The former, not so much.

"It's still difficult," said Carvalho, who gave up his habit in May and continues to wear a nicotine patch to help control his cravings. "Someone can be smoking weed right next to me, and I'm fine. ... If somebody's smoking a cigarette in front of me, I'll have to get up and walk away."

Now, a Duluth researcher is launching a study to seek to discover, in part, what effect marijuana use has on individuals trying to quit tobacco cigarette smoking.

The study will take place in Duluth and the Twin Cities, both prime places, said the researcher, Mustafa al'Absi of the University of Minnesota Medical School's Duluth campus. He was involved in a national study a few years ago, al'Absi said, that included data on marijuana and tobacco use in 10 cities. In four of those cities, the practice of smoking both tobacco and marijuana was more prevalent: San Francisco, Baltimore, Minneapolis and Duluth.

"And that's one reason why we thought this would be a good study for the community," said al'Absi, a behavioral medicine specialist who directs the newly formed Duluth Global Health Research Institute. "Especially at this time when more and more marijuana is becoming available. More and more states are legalizing it. We want to be ahead in knowing how our smokers could still try to quit."

This brings up a dicey subject. For his study, al'Absi needs people who smoke both tobacco and marijuana. But smoking marijuana recreationally still is illegal in Minnesota. Can participants identify themselves as marijuana users without recriminations?

"Well, everything they tell us is confidential," al'Absi said. "We have a federal certificate of confidentiality, which gives us the right to withhold all information."

Al'Absi and others have extensively studied smoking cessation, he said. But little data are available on how marijuana use might play into attempts to quit.

The purpose of studying that is not just to gain information, al'Absi said. The point is to use that information to help people quit smoking - something that's extremely beneficial but extremely difficult.

"If you're using marijuana or other substances, I want to know if that will make a difference in how I treat you," he said. "The research that we're doing here will help answer that question."

Al'Absi knows how difficult it is. Like many, the 55-year-old started smoking as a teenager. He quit around the time, 20 years ago, that he and his family moved to Duluth.

He didn't succeed immediately.

"I tried multiple times," al'Absi said.

Carvalho also experienced relapses. But he has refrained for the past five months, he said last week.

Like al'Absi, Carvalho started smoking as a teenager, and when he decided to quit, he was a pack-a-day smoker. He's using the lightest form of a nicotine patch now, but went beyond recommended lengths of time for each phase of the treatment because his smoking habit had been so entrenched.

For most people, the patch doesn't work all that well, al'Absi said - it has a 10 percent success rate. But it works better for men than for women.

His previous studies show why, al'Absi said. Women tend to experience more psychological symptoms, such as anxiety and depression, when they try to quit. For men, the craving is more chemical, so the nicotine boost from the patch is more likely to help them.

But the bottom line for al'Absi is the effect of stress.

"Stress is a big trigger for addiction," he said. "It goes without saying that people under a high level of stress seek comfort, seek a way to alleviate their negative feelings. And if you're a smoker already, then lighting up is one way to do that."

One size doesn't fit all when it comes to quitting, al'Absi said.

His research feeds into what's known as personalized or precision medicine, in which the treatment plan differs with the individual.

"So that what triggers ... your craving for cigarettes may be different from what triggers my craving," he said. "You have a different life situation. We have different reasons why we smoke."

Al'Absi's study is funded by the National Institutes of Health. About $2 million a year in research funding comes to the medical school's Duluth campus from that source, said Dr. Paula Termuhlen, the dean for the campus.

Such studies give the campus a significant reputation, she said.

"A project where people locally participate, like this, then translates into recognition that in many respects is international," Termuhlen said. "So that when there are problems to be solved they come to Duluth to say, 'Hey, you've got the people there to do it.'"

To get involved

Mustafa al'Absi and his team at the Behavioral Medicine Laboratories of the University of Minnesota Medical School's Duluth campus are looking for participants in their stress response smoking cessation study.

Smokers who are interested in quitting, at least 18 years old, generally healthy and who use marijuana regularly are wanted. Compensation will be provided.

For more information, call (218) 726-8623.