RESEARCH aired at the recent annual meeting of the American Psychiatric Association in San Francisco adds intriguing new data to the controversy over whether stress in itself can cause cancer.
Psychiatrists led by Dr Arnstein Mykletun and colleagues from the University of Bergen in Norway followed up 62,591 participants in Norway’s largest medical survey of a general population, and found a statistically significant relationship between high scores on an anxiety scale completed in 1995 and the later development of premalignant states of disease.
Another recent large study published in the Journal of the National Cancer Institute from the National Institute of Ageing in the US has found that chronic depression can cause cancer. In particular, the researchers found that being despondent for a long time (in their study the low mood had been present for at least six years) almost doubled your risk of getting cancer.
Previously, doctors had found being a depressed smoker increased your chances of getting cancer more than just being a smoker - the theory was depressed smokers inhaled more deeply than the non-depressed, because they craved the antidepressant effect of nicotine.
But in this latest study, by Dr Brenda Pennix and colleagues, the depressed were found to be less likely to be smokers than the non-depressed. Startlingly, this study found getting a long-term depression increased your chances of getting cancer more than taking up smoking!
Given how much we are advised not take up bad habits as a way of avoiding cancer, this greater risk of cancer linked to long-term depression would suggest anyone prone to long bouts of low mood should have the depression treated vigorously. It could almost be said breaking the habit of chronic depression could be even more important than stopping smoking, if you want to avoid cancer.
While smoking is strongly linked to lung cancer, it seemed from this study that melancholy increased the chances of getting any cancer, though depressed women seemed particularly vulnerable to cancer of the uterus.
The authors of this investigation argued depression had not been found to be such a strong risk factor for tumours in the past because previous research did not measure despondency on three separate occasions over a period of six years, as this study did. This allowed the researchers for the first time to pick up the risk of cancer if you have a deep gloom that persists over such a long period of time.
In fact, if you did not have any signs of low mood at all, on any of the three occasions over six years it was measured in this study, you reduced your chances of getting cancer by another 50 per cent, compared with the average person in the rest of the population. But clearly such people, who almost never suffer dips into gloom, are pretty rare; the researchers could find only 186 such up-beat folk in a study population of almost 5,000 people.
But this is not the first time low mood has been suggested to cause cancer. A study done back in the 1980s found that almost 10 per cent of those rated as depressed 20 years earlier had died of cancer, compared with only 5 per cent of the non-depressed.
Other research has found people who get cancer are more likely to have suffered the loss of a major emotional relationship prior to the onset of cancer, and also that those scoring lower on closeness to their family are more likely to develop cancer in the future.
Research has also found that women who are socially more isolated have a five-times greater chance of dying from certain cancers, and are twice as likely to get these cancers in the first place. Unmarried women have a significantly worse death rate from cancer than married women. But exactly why upset should cause cancer remains a mystery. It is well known that depressed people have higher levels of stress hormones in their bloodstream, and these hormones reduce the activity of the white blood cells that patrol the body looking for cancer cells to attack. So depression might reduce the activity of the immune surveillance mechanism everybody has that acts as an early warning system for the first few cancer cells that begin to go out of control, and which normally get detected and consumed by our white blood cells, when they are functioning well.
There is a sense in which depression produces immune suppression in a similar way to AIDS, and as AIDS is linked to a higher rate of certain cancers, this might be why depression is, as well.
Support for this theory also came from separate new research presented at the same American Psychiatric Association conference that found immune activity was dramatically reduced in adults suffering from depression. The study, by Dr Sandra Nunes and colleagues from the University of Estadual De Londrina in Brazil, evaluated various immune measurements in 40 non-medicated adult patients with depression, compared with 34 healthy controls. The researchers found significant reductions in lymphocyte and other white blood cell activity responses, antibody responses and reductions in other acute inflammation phase proteins in the depressed group, compared with controls.
Two previous studies have found an association between lymphomas and malignant melanomas and psychological stress, which are some of the most intriguing findings in the field, as they suggest a mediating link between immune system function, cancer and psychological distress.
One study done in 2000 examined the effect of the stress of bereavement in 6,284 Jewish Israelis who had lost a son in war or in an accident between 1970 and 1977. In comparison with the risk for lymphatic and blood cancers of the Israeli population as a whole, the risk was increased for parents whose sons had been killed at war or in accidents. In addition, the risk for malignant melanoma was significantly increased in both groups, and that for cancers of the respiratory tract were increased in parents of sons killed in accidents.
GIVEN we already know from research that socially isolated women are more prone to cancer, it is interesting that other studies have found white blood cell function is significantly worse in women a year after separation or divorce, than in women who continue to be happily married.
Another theory is that it is not so much the depression, but how the depression alters your behaviour, which causes the cancer. Chronically depressed people might not look after their health as much due to poor motivation, and so might abuse alcohol more and eat a poorer diet, producing greater cancer risk. For example, there is some evidence that diets higher in fat cause more cancer and also that depressed people eat fattier diets, perhaps because they derive comfort from such food.
But if low mood can cause cancer and even make the prognosis worse, could this also not mean that changing your mood to a more positive one could be helpful in preventing cancer, or improving the prognosis if you get it? Medical research has indeed found that some of those cancer patients who adopt a "fighting spirit", and who do not avoid confronting the fact they have cancer, develop a significantly better prognosis.
However, the concept of fighting spirit has recently become controversial within the field, as the scientific data on its benefits remains controversial and it is seen as putting too much pressure on cancer sufferers to be up-beat and positive all the time in extremely difficult circumstances. However, those who join cancer support groups are found to live on average nearly a year and a half longer than those who do not. Also, those suffering from cancer who are taught stress-management skills have been shown to improve their white blood cell functioning.
Of particular interest is the finding from previous research that depressed people are more likely to have a family member who has had cancer, plus other studies have found that those related to cancer sufferers have lower white blood cell functioning. It would seem poorer white blood cell functioning could run in families. This would suggest that if you are related to someone who has had cancer, you should pay particular attention to ensuring any low mood you may be prone to does not become chronically established, because this depression could further reduce your vulnerability to lowered immune system functioning.
But given having cancer itself is a chronic and severe stress, with daily reminders of the condition in the form of symptoms or arduous treatments, this latest research suggests perhaps this anxiety in itself plays a role in determining the future prognosis.
The good news is, these latest studies suggest that improving the mental health of cancer patients won’t just help them feel better, it could even assist survival.
In fact, preventing yourself from getting cancer now means not just giving up bad habits like smoking, but developing a lifestyle that reliably enhances your mood.
Raj Persaud is author of Staying sane: how to make your mind work for you, published by Bantam Press, 7.99.