When people talk about addiction, they often think first about its social, emotional, or psychological consequences. However, problematic substance use can also have a profound impact on physical health. Among these effects, one of the most important — and sometimes less understood — is its relationship with cancer. Tobacco, alcohol, and other substances can influence biological processes related to chronic inflammation, cellular damage, immune alterations, and exposure to carcinogenic compounds.
The relationship between addiction and cancer does not mean that every person who uses substances will develop cancer. Cancer is a complex disease influenced by genetic, environmental, immunological, and lifestyle factors. However, there is strong evidence that some substances increase the risk of certain types of cancer, especially when use is frequent, prolonged, or combined with other risk factors.
Tobacco: One of the Most Well-Known Cancer Risk Factors
Tobacco is one of the most important preventable risk factors associated with cancer. Although many people mainly associate it with lung cancer, its impact goes far beyond that. Cigarette smoking and exposure to secondhand smoke cause nearly 9 out of 10 lung cancer deaths, and people who smoke have a risk of lung cancer nearly 25 times higher than those who do not smoke. In addition, tobacco can cause cancer in multiple organs, including the mouth, throat, larynx, esophagus, bladder, pancreas, kidney, cervix, liver, stomach, colon, and rectum.
This damage occurs because tobacco smoke contains numerous chemicals capable of damaging DNA. When DNA is altered and the cell cannot properly repair that damage, mutations can accumulate and favor tumor development. Tobacco also contributes to persistent inflammation and alters the body’s normal defense mechanisms, which may facilitate the progression of precancerous lesions into invasive cancer.
Alcohol and Cancer: A Less Known but Well-Established Relationship
Unlike tobacco, many people do not associate alcohol with cancer. However, alcohol is considered an established human carcinogen. Epidemiological evidence shows that people who consume alcohol have a higher risk of developing several types of cancer, and that risk increases as the amount consumed increases. Even consumption levels considered “light” may increase the risk of some cancers, such as breast cancer.
Alcohol has been associated with cancers of the mouth, throat, larynx, esophagus, liver, breast, colon, and rectum. Links with other tumors have also been described in some studies. One key point is that it is not only “strong” alcoholic drinks that matter: beer, wine, and liquor all contain ethanol, and ethanol is the compound related to increased cancer risk. Therefore, from an oncology perspective, there is no alcoholic beverage that can be considered completely “safe” in absolute terms.
How Can Alcohol Promote Cancer?
The mechanism does not depend on a single pathway. When the body metabolizes alcohol, it produces acetaldehyde, a toxic molecule that can damage DNA and cellular proteins. Alcohol consumption can also increase oxidative stress, alter nutrient absorption, promote chronic inflammation, and modify hormone levels, such as estrogen, which helps explain its relationship with breast cancer.
Alcohol can also make it easier for other carcinogens to penetrate tissues, especially in the mouth, throat, and esophagus. This is important because when alcohol and tobacco are combined, the risk does not simply add up: it can multiply, especially in cancers of the upper aerodigestive tract, such as cancers of the mouth, pharynx, larynx, and esophagus.
Combined Use: When Risks Are Amplified
One of the most concerning scenarios is the combined use of alcohol and tobacco. Both substances can damage tissues that are directly exposed, such as the oral mucosa, throat, and esophagus. Alcohol can act as a solvent, facilitating contact between carcinogenic compounds from tobacco and the cells. At the same time, tobacco provides substances that directly damage DNA.
For this reason, a person who smokes and consumes alcohol frequently may have a much higher risk than someone exposed to only one of these factors. This point is especially important in prevention campaigns, because many people try to reduce one habit while maintaining the other, without knowing that the combination can be particularly harmful.
Other Substances and Cancer: A More Complex Relationship
When discussing drugs other than alcohol and tobacco, the relationship with cancer can be more difficult to establish. Some substances may increase risk indirectly through their effects on the immune system, liver, lungs, sexual behavior, nutrition, exposure to contaminants, or delayed access to healthcare. American Addiction Centers summarizes that drug and alcohol abuse can affect multiple organs and systems, generating important physical complications in addition to psychological and social effects.
In the case of other drugs, such as smoked cannabis, cocaine, crack, opioids, inhalants, or adulterated substances, the relationship with cancer may be more complex and not always as direct as it is with tobacco or alcohol. In some cases, the risk may be related to inhalation of smoke or irritating chemicals, lung or liver damage, chronic inflammation, exposure to contaminants, immune system weakening, or greater vulnerability to infections associated with cancer, such as hepatitis B, hepatitis C, HIV, or HPV.
For example, some forms of consumption may involve pulmonary exposure to smoke or irritating substances. Others may increase the risk of viral infections related to cancer, especially when there are risk behaviors or barriers to medical care. In these cases, the link with cancer is not always direct, but it can be part of a chain of biological and social vulnerability.
Therefore, although not all substances have the same level of evidence as direct causes of cancer, problematic substance use can increase the body’s vulnerability and make prevention, early diagnosis, and timely access to treatment more difficult.
Figure 1. Substance use may influence cancer risk through DNA damage, oxidative stress, chronic inflammation, and cancer-associated viral infections. Tobacco and alcohol have the strongest evidence, while other drugs may contribute indirectly.
Addiction in Patients with Cancer: A Topic That Requires Sensitivity
It is also important to recognize that addiction may be present in people who already have cancer. This can complicate the management of pain, anxiety, sleep, treatments, and quality of life. However, the approach should not be based on judgment or blame. Addiction is a complex condition with biological, psychological, and social components. Identifying it allows healthcare teams to offer support, treatment, and guidance — not punishment.
In modern oncology, discussing substance use should be part of a comprehensive patient evaluation. Reducing or stopping tobacco and alcohol use can improve overall health, decrease future risks, and support better therapeutic decisions. In some cases, this requires professional intervention, psychological support, pharmacological treatment, or specialized programs.
Prevention: Reducing Risk Is Also Part of Cancer Care
Cancer prevention does not depend on a single decision. Not all risk factors are modifiable, but some are. Avoiding tobacco, reducing or eliminating alcohol consumption, getting vaccinated against cancer-related viruses, maintaining regular medical checkups, and seeking help for addiction are actions that can significantly reduce risk.
Current evidence is not meant to create fear, but to provide clear information: tobacco and alcohol use are related to several types of cancer, and reducing exposure can protect long-term health. For many people, the first step is not achieving a perfect change immediately, but recognizing the risk and seeking support.
The relationship between addiction and cancer is a topic that deserves more public discussion. Tobacco remains one of the most important preventable factors associated with cancer, while alcohol, although socially normalized, also has a clear relationship with several tumors. Other substances may contribute directly or indirectly to conditions that increase the body’s vulnerability.
Talking about these risks should not be used to blame people, but to inform, prevent, and support them. Science shows that reducing substance use, seeking treatment for addiction, and strengthening preventive care can be essential steps to protect health and lower cancer risk.
This blog is intended for educational and informational purposes only. It does not replace professional medical advice, diagnosis, or treatment.
Main reference
American Addiction Centers. (2024, December 31). Cancer and addiction: Does substance abuse increase the risk of cancer? American Addiction Centers. https://americanaddictioncenters.org/health-complications-addiction/cancer
Other references:
Jun, S., Kim, J. S., Park, S., Shin, A., & Oh, J. K. (2024). The combined effects of alcohol consumption and smoking on cancer risk: A systematic review and meta-analysis. Cancer Epidemiology, Biomarkers & Prevention, 33(6), 789–799. https://pmc.ncbi.nlm.nih.gov/articles/PMC11164648/
Tang, M. S., Wu, X. R., Lee, H. W., Xia, Y., Deng, F. M., Moreira, A. L., Chen, L. C., Huang, W. C., & Lepor, H. (2022). DNA damage, DNA repair and carcinogenicity: Tobacco smoke versus electronic cigarette aerosol. Mutation Research/Reviews in Mutation Research, 789, 108409. https://pubmed.ncbi.nlm.nih.gov/35690412/
