A person exhales vapor while using an electronic cigarette device in San Francisco. David Paul Morris | Bloomberg | Getty Images

There are two people you should never lie to, Dr. Michael Plisco tells patients, your lawyer and your doctor. The critical-care pulmonologist at Mercy Hospital in St. Louis thinks a patient's lie may have cost his life when he turned up at the hospital after months of feeling ill. By the time Plisco saw man, who was in his 40s, his lungs were so stiff they couldn't push any fluid out, putting him at risk of cardiac arrest. Doctors tried extracorporeal membrane oxygenation, a machine that pumps blood through a person's body while bypassing the lungs and heart. It did not work. The man's organs failed and he ultimately died in September.

The man, whom Missouri state health officials declined to disclose additional details about, initially denied smoking or vaping, Plisco said. As he grew sicker, he finally admitted he was vaping, but wouldn't say what he used. "In his mind, he wasn't hurting himself," Plisco said, adding that if doctors had known earlier, they could have told the man to stop vaping, which Plisco said may have saved his life.

Patients lying

Doctors trying to unravel the mystery cause of a deadly vaping-related lung disease that has killed at least 42 people were running into a problem trying to nail down the cause: Some of their patients were lying to them about what they vaped. That further complicated an already difficult investigation. Tentatively being called EVALI — short for e-cigarette, or vaping, product-use associated lung injury — the disease has sickened more than 2,170 people, most of them young men. What began as a few cases in the spring ballooned into a national public health crisis over the summer. Doctors say the disease is deadly, sending nearly everyone who develops it to the hospital and about half to intensive care. Though the pace of the disease has slowed, it's still wreaking havoc in the U.S., where doctors have identified nearly 200 new cases a week, on average, since mid-September. One 17-year-old patient received a double lung transplant on Oct. 15 after spending more than a month in three hospitals in Detroit.

Likely culprit

U.S. and state health officials have traced the illness to vaping, mostly THC, and so far have identified vitamin E oil as a likely culprit. There might be "many problematic substances causing lung injury," CDC Principal Deputy Director Anne Schuchat told Congress last week. "It may turn out there are only two kinds of people who get this disease: those who vape THC and those who won't admit it," said Dr. Scott Aberegg, a critical care pulmonologist at University of Utah Health. Aberegg has treated more than 30 patients with EVALI so far.

The Food and Drug Administration, which launched a criminal investigation into the outbreak over the summer, has gone to great lengths to emphasize that it's not prosecuting individuals who have vaped THC even if they live in states where it's still illegal. "Let me be clear, [the FDA] is not pursuing any prosecutions associated with personal use of any controlled substances in these cases," Mitch Zeller, director of the FDA's Center for Tobacco Products, told reporters on a Sept. 19 conference call.

Most people lie

Still, many patients were at first reluctant to tell their doctors they vaped THC. Most people, in fact, lie to their doctors at some point, especially about potentially embarrassing information like how much they drink alcohol, their eating habits and exercise. Two surveys published in the Journal of the American Medical Association last year found that 60% to 80% of the 4,510 adults surveyed have withheld key information from their doctor. The most common reasons for withholding these details included not wanting to be judged or lectured, not wanting to hear how harmful their behavior is and embarrassment. That explains why someone might not want to tell their doctor they are vaping THC, even though social acceptance for marijuana is at an all-time high. Two-thirds of Americans said they support legalizing it, according to a 2018 Gallup poll. Thirty-three states and Washington, D.C., have legalized medical use and 11 states and D.C. have legalized recreational use, according to the Marijuana Policy Project.

Negative stigma

But marijuana is still illegal on a federal level and is far from being considered mainstream. Some EVALI patients, even those in critical care, have denied using it until drug tests showed THC in their system, doctors say. The Centers for Disease Control and Prevention has released data on what patients were vaping for 867 of the EVALI cases through Oct. 15. Of those cases, about 86% reported using THC, the psychoactive compound in marijuana. Many said they used both THC and nicotine. Yet 11% said they exclusively used nicotine. Some doctors think it's possible the 11% who say they only used nicotine may be lying. "Each individual patient might have reasons why they don't want it known they're vaping and specifically what they're vaping," said Dr. Ram Koppaka, a medical officer at the CDC's National Center for Immunization and Respiratory Diseases who is working on the outbreak response.

Key information

It's difficult to quantify how many patients are withholding information from doctors or how many cases aren't being counted because a person won't admit that they are vaping — a key piece of information needed to diagnose EVALI, Koppaka said. With the illness making headlines across America, doctors say patients have been more forthcoming in recent weeks about what they vape. People who vape and experience symptoms are now coming in worried they might have the disease, doctors say. EVALI looks and sounds like pneumonia. Symptoms include chest pain, shortness of breath, fever, nausea and vomiting. But it's not an infection. The antibiotics used to clear up pneumonia don't help the vaping illness. And without knowing the person vapes, doctors might pursue the wrong treatment or miss the chance to encourage the person to stop. "Clinicians should be aware there could be this reluctance and to make sure that as they're evaluating patients and asking about their habits that they should do so in a very nonjudgmental, but thorough, way," Koppacka said.

Drug testing

Aberegg treated a man in his 20s for EVALI who repeatedly denied vaping THC until a drug test came back positive. The patient claimed he had vaped CBD, the nonintoxicating compound in cannabis. Unconvinced, Aberegg told the patient how doctors were increasingly treating people for an illness tied to vaping and how important it was to tell him the truth. At that point, tears welled in the patient's eyes. He asked his parents to leave the room, Aberegg recalled. The young man said he was vaping THC to treat underlying abdominal issues. The sicker he felt, the more he vaped. Dr. Melodi Pirzada, who has treated nearly 20 patients for EVALI as chief of pediatric pulmonology at New York University Winthrop Hospital, said doctors need to be certain of what patients vaped — especially those who say it was just nicotine. "What if they are actually hiding they did THC? That's a concern I have," she said.

Nonjudgmental questions