UK Biobank data shows that opioid medications increase the likelihood of developing lung, pancreatic and bladder cancer – the same cancer types previously only linked to opium use.
Summary
UK Biobank data have revealed that codeine, morphine and other opioid painkillers seem to make people more prone to lung, pancreatic, bladder, oesophageal, and head and neck cancer. These cancer types had previously only been linked to opium, a plant-based drug that shares similarities with some opioid medications. The results suggest that prescription opioids should be used only when necessary.
Opioid medications such as codeine, morphine and oxycodone make people more prone to lung, pancreatic, bladder, oesophageal, and head and neck cancer. These cancer types are known to be caused by opium, a drug made from poppy plants. Although some opioids are similar to substances found in opium, the link between opioids and cancer had been unclear.
“The takeaway is that these medications should not be used without clinical necessity,” says Mahdi Sheikh from the International Agency for Research on Cancer in France, who led the study.
Prescription opioids: essential medications
Millions of people are exposed to opioids – so from a public health perspective, it could be a big issue.
Dr Mahdi Sheikh, International Agency for Research on Cancer, France
More than 3 million people in the UK take prescription opioids, figures from 2025 suggest. Many take these painkillers long-term: in 2021, around 1 million UK residents were prescribed opioids for more than three months.
Opioids can be addictive and even deadly if taken incorrectly. Nevertheless, they are often the only option for people who suffer from severe pain, and several are included on the World Health Organization’s list of essential medicines. “[Opioids] are also essential for substitution therapy, for example, for people who use heroin,” Sheikh explains.
Some opioids mimic substances found in opium, a narcotic made from poppies. Opium has long been used as a recreational drug and painkiller, particularly across Western Asia. In 2020, the WHO classed opium as carcinogenic: it can cause cancer of the lung, pancreas, bladder, oesophagus, and head and neck.
Cancer risks mirror those of opium
UK Biobank participants shared information about what medications they take, which helped researchers discover a link between opioids and cancer
Now, Sheikh and his team have found a similar link between opioid medications and ‘opium-related’ cancer types. In their analysis of UK Biobank data, people taking strong opioids such as morphine had a 90% higher cancer risk than people who didn’t take these medications. Weaker opioids such as codeine increased the risk by 30%.
Opioids didn’t seem to be linked to any other cancer types such as breast or prostate cancer. Other types of painkillers such as paracetamol didn’t affect cancer risk.
It might be tempting to assume that opioids cause cancer, just like opium does – but things are likely to be more complicated, Sheikh says. People who take opioids usually have other health conditions and it’s not yet proven that the increased cancer risk is solely down to the opioids.
It urgently warrants further studies, Sheikh says: “Millions of people are exposed to opioids – so from a public health perspective, it could be a big issue.”
A nuanced approach
The study supports careful, individualised decision-making around opioid use rather than fear or complacency.
Professor Faraz Bishehsari, Rush University, US
“The larger message is that the opioid–cancer relationship is likely context-dependent and varies by cancer type, exposure characteristics and biology,” says Faraz Bishehsari from Rush University, US, who calls Sheikh’s study “well-executed and technically strong”. In 2021, Bishehsari’s team found that opioids might in part be behind the increasing number of pancreatic cancer cases in the US.
Sheikh points out that the results shouldn’t put people off taking opioid medications when necessary. “[The study] supports careful, individualised decision-making around opioid use rather than fear or complacency,” Bishehsari says.
