After Linnea Duff learnt at the age of 45 that she had developed lung cancer, she practically encouraged people to ask if she had ever smoked. But in the eight years since, her feelings have soured considerably on the too-frequent question, and she's developed an acute sense of solidarity with fellow patients: smokers, former smokers, and non-smokers alike.

"It's just so inappropriate," says Duff, who believes that people with other serious illnesses don't have to field so many intrusive questions. "Would you ask someone, 'Did you eat too much?' or 'Did you have too much sex?'"

Tobacco ranks at the top of the stigma list when it comes to behaviours that have been linked to cancer. It's a list that continues to lengthen: excessive drinking, sunbathing, exposure to the sexually transmitted human papillomavirus (HPV). Recently, frequent acid reflux has been blamed for a startling increase in the incidence of some esophageal cancers, raising the question of whether people could be criticised for indulging too much in fatty food, alcohol or other heartburn triggers. Cancer patients may be asked about other, even more tangential behaviour, such as their ability to handle stress, says Larry Lachman, a clinical psychologist in Monterey, California, who counsels people with chronic illnesses.

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Lachman recalls speaking to an alternative medicine practitioner shortly after his own prostate cancer was diagnosed in 1997. Lachman, then in training to become a psychologist, was exploring traditional and alternative medicine approaches. He assumed that traditional doctors would be apportioning blame and be judgmental compared with holistic practitioners.

The reverse proved to be true. Lachman spoke to a reflexologist following cancer surgery: "First thing she said to me was, 'Why did you have to bring cancer on yourself? Why did you have to manufacture your tumour?'"

As a long-serving medical reporter, and someone whose own mother died of lung cancer, I have seen all sides of the stigma issue. I first spoke to Duff for an article about drug research studies she had participated in. The mother of three has responded remarkably well to the treatment for her malignancy, now classified as stage 4. As I wrote the piece, I wrestled about whether to include the fact that she had never smoked. Did it matter? Was it relevant to the research- driven story she had to tell?

A few months ago, Michael Douglas inspired plenty of talk when he appeared to indicate that his stage 4 throat cancer was linked to HPV and oral sex. (A spokesman for Douglas later said that the actor was merely discussing HPV as a potential cause.) But it got me thinking all over again about stigma and our society's fixation on blame, and whether insinuations that cancer patients are responsible for their disease will become more common as additional behavioural links are identified.

As a reporter, I believe in the power of health information to educate and hopefully, in some cases, to motivate people to change. I've written umpteen thousand words about sunscreen, giving up smoking, and other cancer prevention efforts. Given our family history, I'm happy that school health classes have transformed my 10-year-old into a walking anti-tobacco poster. But to what degree do these sorts of educational efforts stigmatise, and thus erode compassion for, individuals once they do become ill?

Duff believes that the Douglas discussion illustrates the rather perverse – and for some of the patients involved, quite painful – hierarchy of the cancer blame game. After all, the actor has a well-documented history of smoking and drinking. Duff says the potential HPV connection might actually boost his standing when it comes to stigma. "I think in our current culture that, even though there may have been some snickering behind the scenes, I don't think that oral sex is going to be viewed as negatively as even cigarette smoking," she says.

For every 1,000 men who are smoking at age 65, 89 of them – or nearly one out of 10 – are expected to die of lung cancer within the next decade, according to a 2008 study in the Journal of the National Cancer Institute. (For non-smoking men, the number is four in 1,000.) That's not the sort of Russian roulette I'd be eager to play; I've never smoked. But the data show that even years of lighting up doesn't guarantee cancer – genetics and other environmental exposures are part of the cancer-causing stew, along with a hefty measure of chance.

Judgements about behaviour not only unsettle and stigmatise the patient, but reflect the interrogator's own insecurities. Frequently, those disease detectives are attempting to regain a sense of control amid the inherently random and sometimes unjust world that we all reside in, according to researchers who have studied stigma.

Psychologists refer to this as the "just-world hypothesis", a bias in thinking and perception that was first described by psychologist Melvin Lerner and colleagues more than four decades ago, and which has since been documented in numerous books and articles.

"I think there is a fundamental assumption in our society that the world is a just place, and that bad things don't happen to good people," says Gerald Devins, a stigma researcher and senior scientist at the Ontario Cancer Institute in Toronto. "And I think when bad things happen to good people, it's threatening to everybody."

Already, cancer patients can be their own worst critics, says Timothy Turnham, executive director of the Melanoma Research Foundation. Those with skin cancer beat themselves up about spending too much time in the sun. Then they obsess about why they didn't check out that odd-looking mole sooner. "Not only is it not relevant, but it can be quite painful," Turnham says. "It's a distraction that you really don't need when you are in a fight for your life."

Becky Herry, a 57-year-old nurse, who has stage 4 melanoma, says that some people will lob what she describes as non-questions with a dose of judgement embedded within. "People will say, 'You were always so tanned,'" she says. "I think it's people's own fear. They think, 'How much time did I spend in the sun compared with how much time Becky spent in the sun, and so what is my risk?'"

Not surprisingly, these sorts of lines of questioning can exacerbate the emotional roller coaster of cancer treatment. A recent study found that at least one-third of men with colon cancer experienced some degree of stigma or self-blame related to their malignancy. That group appeared to be more vulnerable to depression as well, the researchers found. The stigma-depression link also has been identified in lung-cancer patients, according to another recent study. Higher levels of perceived stigma correlated with more acute depression.

Stigma also can undercut research spending, as the US National Lung Cancer Partnership reveals in its stark 2012 analysis. Each year, nearly 157,000 Americans die of lung cancer, compared with 49,380 from colon cancer and 39,970 from breast cancer. Yet far less research cash is spent per lung-cancer death – $1,490 (£934) compared with $6,339 (£3,960) for colon cancer and $21,641 (£ 13,516) for breast cancer.

And no price can be attached to the sense of isolation, for patients and their loved ones. When my mother's tumour was diagnosed at the age of 45, my younger sister was partly through her high-school education. She was sworn to secrecy, navigating the hallways of adolescent angst pretending all was fine at home. I was attending college a plane journey away and was less emotionally circumscribed, able to share my fears with friends who wouldn't cross paths with my mother in the shops.

But it is "childhood magical thinking," as Lachman describes it, that good behaviours provide cancer immunity. The psychologist, who treats a lot of patients with cancer, recounts how unsettled his friends and family were by his own diagnosis. He adhered to a vegetarian diet and ran five miles several times a week; he was diagnosed with prostate cancer at the age of 39. The average age for diagnosis: 67.

For 18 years and counting now, I typically say only that my mother died of cancer. If pressed, I will specify that she died of lung cancer. And then, preferring to head off the inevitable follow-up, I add: "And yes, she did smoke."

The tumour was found by serendipity; a scan for an unrelated thyroid operation had revealed a worrisome spot on her lungs. After her diagnosis, a good chunk of her lung was removed. And yes, she did stop smoking after surgery, another question I tend to parry in advance. She bought us time, the blessing of six more years, with no sign of cancer on numerous scans. Until it returned, the cancer cells widely scattered and untreatable.

My mother was more than a smoker. She was an incessant reader who loved to travel and wore clothes elegantly on her slender frame. She became a health-food nut before it was cool, baking granola and buying natural peanut butter that my sister and I hated to stir. Because she died at the age of 51, she was never able to enjoy my husband's wry sense of humour or my son's ebullience. Was her death just desserts, or just tragic? If people would just stop implying that this is an underlying question, I wouldn't be forced to provide the answer.

A version of this article appeared on Slate.com