A Notable Survey of Cancer Conspiracy Beliefs

In an age when misinformation spreads online as quickly as viruses, a humorous study addressing cancer conspiracy beliefs and opposition to vaccination attracted criticism.

"Everything Causes Cancer? Beliefs and Attitudes Towards Cancer Prevention Among Anti-Vaxxers, Flat Earthers and Believers in Empty Claims: An Online Cross-Sectional Survey" was the title of a study in The Brisith Medical Journal (BMJ) published on 21 December 2022.

The authors explained that they set out to assess "patterns of cancer beliefs among people who believe in conspiracies, reject COVID-19 vaccination or prefer alternative medicine". They recruited participants through social media and online discussion platforms, then asked about actual and supposed cancer causes. Nearly half of respondents agreed that "It seems that everything causes cancer" .

Across all participants, the researchers reported that awareness of actual cancer causes exceeded belief in cancer conspiracy theories. Awareness of actual causes was also lower among unvaccinated participants and conspiracy-group members than among their counterparts. The researchers highlighted "a direct link between digital misinformation and potentially misguided health decisions resulting from it" as a concerning finding.

Reactions and Criticism

BMJ said on Twitter, "The study highlights the difficulty society faces in distinguishing actual from supposed causes of cancer". However, both the study and journal drew criticism.

Clare Craig, a British pathologist specialising in cancer diagnosis, commented, "This is a terrible paper attempting to smear people who have concerns about COVID vaccines". Prof. Norman Fenton of Queen Mary University of London also strongly criticised the study and its methodology on Twitter.

Laura Costas, a medical epidemiologist at the Catalan Institute of Oncology in Barcelona, Spain, and a study author, said that many social-media critics focusing on COVID-19 vaccination illustrated the study’s point: misinformation spreads widely online.

"Most comments focused on spreading COVID-19 myths, which were not the study’s direct subject, and questioned the motivations of the BMJ authors and scientific community, assuming a shared malicious hidden agenda. They stressed the need for critical thinking, a feature of the scientific method, but dogmatically rejected every piece of information from official sources. Society struggles to distinguish actual from supposed or unproven cancer causes amid mass information. We therefore designed the study with a degree of satire, in keeping with the spirit of the BMJ Christmas issue."

BMJ has a long tradition of publishing a Christmas issue featuring original, satirical and unconventional studies.

Study Details

Costas and colleagues recruited participants from online forums such as 4chan and Reddit, known for controversial content posted by anonymous users. Data also came from well-known Spanish forums ForoCoches and HispaChan. Costas said these sites were selected because the researchers expected "conspiracy beliefs to be more common". The forums yielded 1494 participants: 209 unvaccinated against COVID-19, 112 preferring alternatives to conventional medicine and 62 who reported believing that the Earth is flat.

The team assessed beliefs about actual and unproven cancer causes using risk-factor questions from the Cancer Awareness Measure (CAM) and CAM–Mythical Causes Scale (CAM-MYCS). Responses on both used a five-point scale from "strongly disagree" to "strongly agree".

CAM assessed perceptions of 11 factors known to increase cancer risk:

1. Active or passive smoking
2. Alcohol consumption
3. Low physical activity
4. Eating red or processed meat
5. Sunburn during childhood
6. A family history of cancer
7. Human papillomavirus (HIV) infection
8. Being overweight
9. Being aged 70 or older
10. Low fruit and vegetable consumption

Related topic: What Are the Causes of Cancer, Briefly?

The researchers explained that CAM-MYCS included 12 questions about perceived risks from supposed cancer causes—things commonly believed to cause cancer but lacking supporting scientific evidence. Items included:

• Drinking from plastic bottles
• Artificial sweeteners or additives and genetically modified foods
• Microwave ovens
• Using aerosol containers, mobile phones and cleaning products
• Living near power lines
• Feeling stressed
• Experiencing physical trauma
• Exposure to electromagnetic frequencies or non-ionising radiation, including Wi-Fi, radio and television

The most commonly endorsed mythical cancer causes were products containing additives (63.9%) or sweeteners (50.7%), feeling stressed (59.7%) and genetically modified foods (38.4%).