Does stress or emotional upset cause cancer?

• Work stress: 12 studies in Europe followed more than 116,000 men and women for about 12 years; people with high-strain jobs did not develop cancer more often than others ^[1].
• Depression and anxiety: 18 studies with more than 300,000 people found no link between depression or anxiety and cancer overall, or breast, prostate and bowel cancer. Depression and anxiety were linked slightly more often to lung cancer and smoking-related cancers, but when smoking, alcohol and weight were taken into account, this link became much smaller ^[2].
• Breast cancer: in a study of 106,000 women in the UK, the level of stress and difficult life events in the previous 5 years, such as divorce or losing loved ones, had no consistent link with breast cancer ^[3].

Not all studies have had the same result: some reviews have reported links between stress and certain cancers, such as lung or bowel cancer ^{[6, 7]}. Studies of this kind look at people's habits and feelings and cannot on their own show that stress itself was the cause; for this reason the US National Cancer Institute says the relationship between chronic stress and cancer is not yet clear ^{[4, 6]}.

Even when stress seems to be linked to cancer, the relationship may be indirect: someone under pressure for a long time may smoke, overeat, become less active or drink alcohol, and these themselves raise the risk of some cancers ^[4]. The same pattern was seen in the large study of depression and anxiety ^[2].

So the most effective way to lower the risk is to deal with these habits: stopping smoking, cutting down on or stopping alcohol (Does alcohol cause cancer?), being more active and keeping a healthy weight (Does obesity cause cancer?). Long-term stress also does other harm, such as digestive problems, heart disease, high blood pressure, a weaker immune system, poor sleep, depression and anxiety; so reducing it is worthwhile, quite apart from cancer ^[4].

In experiments on animals and on cancer cells in the laboratory, stress hormones have been able to increase tumour growth and spread ^[4]. But in people, the evidence that stress directly affects how long patients live is weak overall ^[4]. In a study of women with breast cancer that had spread, weekly group psychological support sessions improved mood and pain but did not change survival ^[8].

On current evidence, there is no convincing proof that a person's attitude affects their risk of getting cancer or dying from it ^[5]; so if cancer comes back, this evidence does not show that the reason was your "worrying" or "not being positive". Caring for your emotional health matters because it makes this time lighter and easier to bear. Read about recurrence and follow-up: What is cancer recurrence and how is it followed up?

Fear, anxiety, sadness and worry that the illness will come back are common during cancer, and if they become severe or last a long time, help can and should be sought ^{[4, 9]}. The American Society of Clinical Oncology guideline recommends that all patients be given information about depression and anxiety and, depending on how severe the symptoms are, be offered approaches such as talking therapy (cognitive behavioural therapy), mindfulness-based stress reduction programmes, regular exercise and, if needed, medicines ^[9]. Some organisations recommend that all patients be checked for distress with a simple questionnaire after diagnosis and during and after treatment ^[4]. A fuller guide: Anxiety, depression and fear of cancer coming back.