PNI stands for psychoneuroimmunology – where ‘psycho’ means the mind, ‘neuro’ the nervous system, and ‘immunology’ means the body’s immune defenses. This new medical discipline focuses on the mechanisms by which the mind is able to affect the body and takes a whole-body approach to these systems rather than looking at them separately.
PNI began with the surprising discovery that the body’s immune system can be conditioned to react to things that would normally have no effect on it. The finding was made by US researcher Robert Ader when he was working on conditioning in mice. One experiment involved giving the mice cyclophosphamide – an immune suppressant that severely reduced their ability to produce anti bodies to invading organisms – in a saccharin-flavored drink. What Ader discovered was that similar effects on the immune system occurred in conditioned mice when they were given the sweet drink on its own, without the drug. Their immune systems had ‘learned’ to respond to the drink as if it were the drug associated with it.
Researchers began to wonder if they could pair a drug that boosts the immune system with another substance and use the learned response to achieve beneficial effects using lower drug doses. In a later experiment, the) did just that. A woman with lupus, an immune disorder that damages joints, skin, and internal organs, at first took all her doses of medicine together with cod liver oil and rose perfume. Over a 12-month period, she came to need only half as many doses of medication as expected if the doses were alternated with cod liver oil and perfume; she continued this regime for five years, and her condition improved.
Influencing immunity
Not so long ago, this phenomenon would have seemed baffling because the immune system and the nervous system were thought to be quite separate. Immunology was based on cells and molecules fighting invading organisms, and the idea that these apparently automatic chemical processes could be learned seemed absurd.
Recently, however, biologists have discovered numerous ligands that effectively bind the nervous and immune systems into one complex, interactive whole. Things that happen at the very ‘ highest’ level of the nervous system – our thoughts, beliefs, and perceptions can affect individual molecules in the furthest reaches of the body and vice versa. Although it seems hard to imagine how difficult periods in our lives could affect our ability to fight illness at the cell level, research shows that this is indeed the case. In one study, 40 medical students were assessed six weeks before their final exams and again during the exams. Their levels of distress increased between the first and second assessments, and the number and activity of a particular type of immune cell were significantly lower during the exam period. PNI is the science of discovering exactly how this sort of effect comes about.
Mind and body pathways
Many of the pathways linking mind and body have yet to be revealed, but two routes are well understood. One lies in the wiring of the nervous system: branches of the peripheral nervous system have been shown to extend right into immune system organs and tissues such as the spleen and bone marrow. Signals sent from the brain to these areas may stimulate or inhibit them directly. The second route is via chemicals and messenger cells that carry information from one part of the body to another. The various types were once firmly assigned to a particular body system: neurotrans matters and endorphins, the chemical messengers in the brain were associated with the nervous system; hormones with the endocrine system; and cytokines (immune cells) with the immune system. But now they are all revealed to be part of a single family of messenger cells, which mediates between the systems as well as working within them.
The knock-on effect of molecular changes from one system to another explains why a condition such as depression – normally thought of as an illness of the mind – can have profound effects on other parts of the body. A common chemical change in people with depression and dementia is a drop in the levels of noradrenaline, a neurotransmitter in the brain that stimulates brain cells and helps us to generate thoughts and perceptions. A drop in noradrenaline not only causes mental sluggishness but reduces the nerve activity that stimulates tissues to keep certain immune cells circulating. So, instead of seeking out and fighting bacteria and viruses, the inactive immune cells allow infections to thrive.
Effects of anxiety and emotion
Anxiety damps down the immune system in a similar way. The brain reacts to anxiety in the same way that it reacts to fear by telling the adrenal glands (situated above the kidneys) to prepare the body for fight or flight. The adrenals respond by flooding the body with cortisol, which has several useful effects in an emergency: it thickens the blood, helping to reduce catastrophic bleeding in the event of injury; it tenses the muscles in preparation for fighting or fleeing; and it heightens mental alertness.
But while all this is happening, the everyday business of body maintenance is put on hold, such as the tracking down and destruction of foreign or errant ceLs, including any that won’t stop dividing when they should and may, therefore, produce cancer. Anxiety is certainly not the cause of cancer, but it may, in this way, allow a tumor to escape destruction at an early stage. In contrast, positive mental experiences can stimulate the immune system, helping to keep illness at bay. Laughter, for example, brings about profound changes in many parts of the body – it relaxes the muscles, increases blood flow, and stimulates the production of ‘feel-good’ neuro transmitters. Anger and hostility, on the other hand, reverse these effects. Anger is thought to have a negative impact on the body because it raises the levels of stress hormones, which damage the linings of blood vessels. This may cause inflammation and the formation of scar tissue, slowing down the passage of blood and encouraging the formation of clots, which can lead to a heart attack. Feeling angry in inappropriate situations is not going to cause you harm, but if you can learn to laugh at frustrations rather than get upset about them, you may be helping yourself to a longer and healthier life.
BEATING A COLD
When you feel a cold coming on, the two things you are least likely to feel like are having a good laugh and getting romantic with your partner. But it may be well worth making an effort as both these activities can help to ward off infections by boosting the activity of your immune system. Laughter works by reducing the levels of stress hormones in the blood, which slow down the immune cells responsible for searching out and destroying viruses. Having a cuddle may also benefit the immune system by raising levels of the ‘attachment’ hormone, oxytocin. This hormone is produced when people show affection {as well as during orgasm}, and it is the foundation of the mother-child bond. Babies who do not get enough physical affection in the weeks after birth fail to produce normal amounts of oxytocin, and that may be one reason why they tend not to thrive and succumb more easily to infections.
CORTISOL AND THE BODY’S DEFENCES
The immune system ‘army’ has an important battalion of natural killer (NK) cells, whose role is to search out and destroy mutant or alien cells. NK cells are activated as part of a sequence of hormonal and chemical changes triggered by injury or disease. The ‘alarm signal’ that gets them working is a sudden rise in the stress hormone cortisol. If cortisol levels stay high, however, the NK cells become depleted and are no longer so effective. A study of women with breast cancer found that those whose cortisol levels remained at a high level survived, on average, for three years after diagnosis, while those whose cortisol levels rose and fell in a normal way survived over a year longer. Women with high cortisol levels were also found to have fewer NK cells. Helping to keep stress – and cortisol – down to normal levels may be one reason why relaxation techniques can help cancer patients.
The PNI revolution
PNI is helping to bring about a quiet revolution in scientific thinking. In conventional medical research, the fact that many body processes at a molecular level could be reproduced in a test – -tube reinforced the idea of the body as a machine. This approach has undoubtedly been very successful in giving rise to drugs and treatments for many diseases. However, the more success doctors have had in curing specific disorders, the more their patients seem to complain of non-specific problems like general tiredness, depression, and varieties of vague malaise that do not match the usual textbook descriptions of illnesses that they have been trained to deal with.
The idea that systems in the body and brain are linked to form a grated whole helps us to make sense of this modern epidemic. Treatments that concentrate solely on the part that needs ‘fixing’ may cure a specific disease but ignore other aspects of mental and physical well-being. Holistic practitioners have always recognized this, and PNI is finally underpinning their approach with a scientific basis.
