Stress can reach your immune cells, but positive thinking still can’t cure cancer

Key takeaways

• In 1975, University of Rochester researchers showed that rats could learn to suppress their own immune responses, a finding that helped launch the science of mind-body links.
• In a British study of about 400 volunteers given cold viruses, the more stress people reported, the more likely they were to come down with a cold.
• The American Heart Association concluded in 2014 that depression is a risk factor for worse outcomes after a heart attack or similar heart emergency.
• Placebo pain relief runs partly on the brain’s own opioid chemistry, though the research centers on symptoms such as pain, not on curing disease.
• A study of 1,093 people with head and neck cancer found that emotional well-being was not linked to survival, one more reason not to blame anyone’s attitude for their illness.

In the early 1970s, psychologist Robert Ader was running a taste-aversion experiment at the University of Rochester. Rats drank sweetened water while getting a drug that upset their stomachs, so they learned to avoid the taste¹.

The drug also happened to weaken the immune system. When Ader kept offering the sweet water after the drug was stopped, some of the rats died¹.

Ader suspected the rats’ brains had learned to turn down their immune defenses on cue. He tested the idea in animals that had been deliberately immunized, and the 1975 paper reporting the results in Psychosomatic Medicine backed him up¹.

At first, many scientists dismissed the notion that the brain could steer immunity¹. Ader gave the new field its name: psychoneuroimmunology, the study of how the mind, nerves and immune system talk to each other. Its ideas have since spread far beyond psychiatry, into many branches of medicine¹.

Natural health has always taught that mind and body are one system. Science now agrees in ways you can measure. It also shows where that idea gets stretched too far. Here is what’s established, what’s promising and what’s myth.

Stress made healthy volunteers more likely to catch a cold

From 1986 to 1989, researchers at Britain’s Common Cold Unit in Salisbury ran an unusual test. They measured stress in about 400 healthy adults, then put drops containing one of five cold viruses into their noses².

The volunteers were quarantined and examined every day. A cold counted only if a doctor saw symptoms and lab tests confirmed the virus had taken hold².

Psychologist Sheldon Cohen of Carnegie Mellon University and his colleagues reported the results in the New England Journal of Medicine in 1991. The pattern was graded: each step up in stress came with a higher chance of getting sick, and it held for all five viruses³.

The link was not explained by the obvious suspects. It held after the team accounted for age, sex, education, allergies, body mass index, season and existing antibodies. Smoking, drinking, sleep, exercise and diet did not explain it either³.

Later studies by Cohen’s group found that the kind of stress mattered. The longer a stressful problem lasted, the higher the risk. Trouble with family or friends, or being out of work or underemployed, for a month or more stood out³. People who filled more social roles in their lives caught fewer colds³.

A 2012 study in PNAS offered one explanation. Normally, the stress hormone cortisol tells immune cells to calm inflammation. After long-term stress, the cells seemed to stop listening, so inflammation ran hotter once a virus arrived⁴.

In that study of 276 volunteers, a recent major stressful event was tied to roughly double the odds of a cold⁴. The authors suggested the same broken “off switch” may help explain other stress-linked inflammatory diseases, an idea that still needs testing⁴.

Hard childhoods show up in adult health records

For a landmark study published in 1998, researchers mailed a questionnaire to 13,494 adults who had completed a standard medical exam at a large health plan. Of them, 9,508 answered, a 70.5% response rate⁵.

The survey asked about seven kinds of childhood adversity. They were psychological, physical or sexual abuse; violence against the mother; and living with someone who abused alcohol or drugs, was mentally ill or suicidal, or had been in prison⁵. More than half the respondents reported at least one⁵.

The 1998 paper by Dr. Vincent Felitti and colleagues found a dose-response pattern. People with four or more kinds of adversity had 4 to 12 times the risk of alcoholism, drug abuse, depression and suicide attempts compared with people who had none⁵. Heart disease, cancer, chronic lung disease and liver disease also rose with each added category⁵.

The CDC still tracks these adverse childhood experiences, or ACEs. Its 2019 report covered 144,017 adults surveyed in 25 states from 2015 to 2017. Of them, 60.9% reported at least one ACE and 15.6% reported four or more⁶. Applying those patterns to 2017 national figures, the agency estimated that preventing ACEs could potentially avoid up to 1.9 million cases of coronary heart disease and 21 million cases of depression⁶.

Those estimates come with limits the CDC authors spelled out. The surveys depend on memory, capture one moment in time, and cannot prove cause and effect⁶. An ACE count describes risk across a population. It is not a forecast for any one person.

The more hopeful half of the story is prevention. The CDC says safe, stable and nurturing relationships help children thrive, and that therapy and family-centered services can reduce harm when adversity has already happened⁷.

Depression is now counted as a heart risk

In 2014, an American Heart Association panel reviewed 53 studies and four meta-analyses (studies that pool the results of other studies). All followed people after an acute coronary syndrome, the medical term for a heart attack or a dangerous episode of blocked blood flow to the heart⁸.

The panel concluded that the weight of the evidence supports depression as a risk factor for death and new heart problems after these events⁸. Depression is common among the estimated 15.4 million American adults who had coronary heart disease at the time⁸.

How might low mood hurt the heart? Researchers point to stress hormones, changes in the nerves that set heart rhythm, stickier blood platelets and inflammation. Behavior matters too: depression is linked to smoking, inactivity and skipped medicines, all of which slow recovery⁹.

There is a catch. In a commentary on the statement, Northwestern University psychologist Bonnie Spring noted that there was no compelling evidence yet that treating depression helps people live longer after a heart event⁹. Depression care is still worth seeking, because feeling better matters on its own.

Emotion can also strike the heart suddenly. The AHA describes broken heart syndrome, in which intense stress, such as grief, a breakup or even a happy shock like a lottery win, briefly weakens the heart’s main pumping chamber¹⁰. It is more common in women and is thought to come from a surge of stress hormones. Most people recover fully within weeks¹⁰.

It causes chest pain and shortness of breath and can be mistaken for a heart attack¹⁰. No one should try to sort that out at home. Call 911.

Placebo responses run on real brain chemistry

For decades, “it’s just a placebo” meant “it isn’t real.” Brain research has changed that view.

A 2015 review in Nature Reviews Neuroscience by Tor Wager and Lauren Atlas described placebo effects as health changes that come from the brain’s response to the setting of care. That setting includes the pill, the ritual, the clinician and the expectation of relief, shaped by learning and past experience¹¹.

These effects use the body’s own chemicals. When researchers blocked natural opioids with the drug naloxone, placebo pain relief faded in the brain’s pain systems. In Parkinson’s disease, expectation changed both symptoms and dopamine activity in the brain¹¹.

Most of the evidence the review covers involves pain, along with symptoms such as the movement problems of Parkinson’s disease¹¹. Showing that a placebo changes how you feel is not the same as showing it fixes the disease underneath.

That distinction cuts two ways. The calm, attentive care many natural-health practitioners offer may ease symptoms through these same pathways, which is a real strength. It is also why feeling better after a remedy does not prove the remedy fixed what was wrong, and why fair trials compare a treatment against a placebo.

Where “mind over matter” goes too far

The mind-body link has a shadow. If stress can affect illness, it is a short step to believing that sick people brought it on themselves, or could think their way out.

Cancer has been the hardest test of that belief. In a 2007 study in the journal Cancer, University of Pennsylvania researcher James Coyne and colleagues analyzed data on 1,093 people with head and neck cancer, drawn from two earlier studies. During the study period, 646 of them died¹².

Patients’ emotional well-being did not predict who lived longer, even after the team accounted for sex, tumor site and stage¹². “The hope that we can fight cancer by influencing emotional states appears to have been misplaced,” Coyne said¹². He added that therapy and support groups can still help people cope and connect, just not live longer¹².

The National Cancer Institute’s review of the wider research lands in a similar place. Lab and animal studies suggest chronic stress hormones may help some tumors grow and spread. In people, though, evidence that stress directly shortens cancer survival is still weak overall, and whether stress causes cancer is unclear¹³.

So hold two truths at once. Your feelings affect your body. Your feelings are not the reason you got sick, and a brave face is not a treatment plan. A companion article on the desire for personal control explores that tension in depth.

What mind-body practices can do

The National Center for Complementary and Integrative Health (NCCIH) defines mind and body practices as techniques that work through brain-body interactions. On a page updated in 2025, it sorts them by their main route: the mind (meditation, mindfulness, music), the body (acupuncture, massage, spinal manipulation) or both (yoga, tai chi, dance)¹⁴.

Meditation has the deepest research. A 2018 analysis of 142 groups with more than 12,000 participants found mindfulness worked better than no treatment for anxiety and depression, and about as well as other proven therapies¹⁵. A 2020 review of 14 studies linked a program called mindfulness-based stress reduction with lower blood pressure in people with high blood pressure, diabetes or cancer¹⁵.

For sleep, a 2019 analysis of 18 studies found mindfulness beat sleep education but did no better than cognitive behavioral therapy or exercise¹⁵. NCCIH adds that tai chi appears to improve balance and may ease knee arthritis symptoms, and that yoga may help low-back pain, neck pain, anxiety and depressive symptoms¹⁴.

These practices are not risk-free. A 2020 review of 83 studies found that about 8% of meditation participants had a negative effect, most often anxiety or depression, a rate similar to talk therapies¹⁵. NCCIH advises asking about a teacher’s training and never using these practices to put off seeing a clinician¹⁴.

For readers who value natural health, the strongest finding may be the simplest. The tools that help most are ones you already own: attention, breath, movement and other people. Published articles on meditation groups and contemplative practices cover the details.

What’s proven, what’s promising and what’s myth

Claim	Evidence rating	What the research shows
Ongoing stress raises your odds of catching a cold	Strong evidence	Graded link across five viruses in controlled exposure studies34
Childhood adversity is linked to adult disease	Strong evidence of a link	Large surveys show dose-response patterns; cause is harder to prove56
Depression worsens outcomes after a heart attack	Strong evidence	AHA review of 53 studies and four meta-analyses8
Treating depression helps heart patients live longer	Not enough evidence	Not shown yet; treatment still eases suffering9
Placebo pain relief uses the brain’s own chemistry	Strong evidence	Blocked by naloxone in lab studies11
Placebos reverse the disease itself	Not enough evidence	Research centers on pain and other symptoms11
Mindfulness eases anxiety and depression symptoms	Strong evidence for symptom relief	Beat no treatment and matched other proven therapies in a large analysis; study quality varies15
Mindfulness lowers blood pressure	Promising but early	Benefit seen in reviews; specific effects not established15
Stress causes cancer	Not enough evidence	Human studies conflict13
A positive attitude helps you survive cancer	Evidence says no	No survival link in 1,093 head and neck cancer patients; NCI calls stress-survival evidence weak1213

A two-minute daily mind-body check-in

This short routine is built from the findings above. It is a way to notice patterns, not a diagnosis. Do it at the same time each day, and jot answers in a notebook or phone.

1. Body scan. Sit still and notice your jaw, shoulders and stomach. Rate your tension from 0 to 10.
2. Sleep. Write down roughly how many hours you slept and whether you woke rested.
3. Mood in one word. Pick a word, not a score. “Flat” and “wired” tell you different things.
4. Connection. Did you have one real conversation today? Social variety showed up as protective in the cold studies.
5. Movement. Note any walk, stretch or activity, even a short one.
6. One small reset. Take a few slow breaths, step outside, or do your usual meditation or prayer.
7. Weekly look-back. Once a week, scan your notes for patterns, such as headaches after tense days or a cold after a hard stretch.

Questions readers ask

The bottom line

The old natural-health conviction that mind and body are one system has held up well. Stress can change immune function, hard childhoods leave marks on adult health, depression weighs on the heart, and expectation can trigger the brain’s own painkillers.

The same science draws a firm line. Feelings influence illness but do not explain all of it, and no attitude has been shown to cure cancer. Use mind-body practices to feel better and live better, keep proven treatment in place, and let go of any guilt about getting sick.

Related reading

• Tai chi, prayer and journaling: what research can measure and what it can’t
• What meditation groups can do, and what they can stir up
• Spiritual well-being shows up in health data, and so does spiritual struggle
• Taking charge of your health helps, until it turns into blame

Sources

1. University of Rochester Medical Center. “Robert Ader, Founder of Psychoneuroimmunology, Dies.” URMC Newsroom, 2011. urmc.rochester.edu
2. Carnegie Mellon University Common Cold Project. “British Cold Study.” Carnegie Mellon University. cmu.edu
3. Cohen S. “The Pittsburgh Common Cold Studies: Psychosocial Predictors of Susceptibility to Respiratory Infectious Illness.” International Journal of Behavioral Medicine, 2005;12(3):123-131 (summarizes Cohen, Tyrrell & Smith, New England Journal of Medicine, 1991). cmu.edu
4. Cohen S, Janicki-Deverts D, Doyle WJ, et al. “Chronic Stress, Glucocorticoid Receptor Resistance, Inflammation, and Disease Risk.” Proceedings of the National Academy of Sciences, 2012;109:5995-5999. cmu.edu
5. Felitti VJ, Anda RF, Nordenberg D, et al. “Relationship of Childhood Abuse and Household Dysfunction to Many of the Leading Causes of Death in Adults: The Adverse Childhood Experiences (ACE) Study.” American Journal of Preventive Medicine, 1998;14(4):245-258. experts.azregents.edu
6. Merrick MT, Ford DC, Ports KA, et al. “Vital Signs: Estimated Proportion of Adult Health Problems Attributable to Adverse Childhood Experiences and Implications for Prevention, 25 States, 2015–2017.” CDC, Morbidity and Mortality Weekly Report, 2019. cdc.gov
7. Centers for Disease Control and Prevention. “Preventing Adverse Childhood Experiences.” CDC, 2024. cdc.gov
8. American Heart Association. “Depression as a Risk Factor for Poor Prognosis Among Patients With Acute Coronary Syndrome: Top Things to Know” (Lichtman JH, et al., Circulation). AHA Professional, 2014. professional.heart.org
9. Spring B. “Depression: A Risk Factor and Two Riddles about Poor Prognosis in ACS.” American Heart Association Professional, 2014. professional.heart.org
10. American Heart Association. “Is Broken Heart Syndrome Real?” AHA, reviewed 2024. heart.org
11. Wager TD, Atlas LY. “The Neuroscience of Placebo Effects: Connecting Context, Learning and Health.” Nature Reviews Neuroscience, 2015;16(7):403-418. nature.com
12. American Cancer Society. “Cancer Survival is Not Influenced by a Patient’s Emotional Status” (press release on Coyne JC, et al., “Emotional Well-Being Does Not Predict Survival in Head and Neck Cancer Patients: A Radiation Therapy Oncology Group Study,” Cancer, 2007). American Cancer Society Pressroom, 2007. pressroom.cancer.org
13. National Cancer Institute. “Psychological Stress and Cancer.” NCI, reviewed 2022. cancer.gov
14. National Center for Complementary and Integrative Health. “Mind and Body Practices.” NIH, updated 2025. nccih.nih.gov
15. National Center for Complementary and Integrative Health. “Meditation and Mindfulness: Effectiveness and Safety.” NIH, 2022. nccih.nih.gov