In the Oxford English Dictionary the definition of a placebo is a medicine or procedure prescribed for the psychological benefit to the patient rather than for any physiological effect.

But when we accept that the body and the brain are not separate, that they are inextricably linked, with our mental and emotional state intricately bi-directionally entangled with our physical health, this definition becomes a bit of an oxymoron! As soon as there is a psychological benefit there will also be a physiological effect and vice versa.

The extended definitions of placebo are: A substance that has no therapeutic effect; and A measure designed merely to humour or placate someone. The first of these by definition rules out a placebo having any real impact on the physical or mental health of a patient: Placebo is defined as useless.

The second is probably closer to the meaning that scientists now think of when they administer placebos in clinical trials.  And of course the placebo is a huge thorn in the side of pharmaceutical companies' as over and over and over again, clinical trials have a nasty habit of demonstrating that placebos really work.

But let’s consider the impact of placebo and nocebo in the context of services rather than substances. Dr Lissa Rankin studied medicine for twelve years before practicing as an OB/GYN physician in a conventional medical practice for eight years. Since 2007, she has been working in integrative medicine. She has pulled together extensive evidence on the power of the placebo and the nocebo which demonstrates that the tendency to be influenced by what we believe to be true extends to our health through our attitudes towards, and expectations about, the impact pharmacological drugs will have, and our trust (or distrust) in our healthcare providers.

The results are that for those who have great faith in the wisdom and words of their doctors or other therapists, what they are told by these trusted experts may become a self-fulfilling prediction. She writes: When we pronounce upon someone with statistics like 'Nine out of ten people with your condition die in six months' or 'you have a twenty percent chance of five-year survival,' is this far from the voodoo practices of some native cultures? Are we cursing them, triggering fear responses in their mind, and causing their minds to activate stress responses, when the body most needs relaxation responses?

Epigeneticist Dr Bruce Lipton echoes these sentiments writing: Troublesome nocebo cases suggest that physicians, parents, and teachers can remove hope by programming you to believe you are powerless.

Rankin hypothesises that at least part of the success reported by patients receiving alternative or complementary therapies derives from the beliefs the patients have about their efficacy as well as the dual attitude, attention and intention of the therapist. The practitioner can have a huge positive (or negative) impact on the mental and emotional state of the patient and hence on their physiological state. Lipton notes that: If medical researchers could figure out how to leverage the placebo effect, they would hand doctors an efficient, energy-based, side effect-free tool to treat disease.

In Cure, Jo Marchant, PhD in Genetics and Medical Microbiology, writes, At the heart of almost all the pathways I’ve learned about is one guiding principle: if we feel safe, cared for and in control – in a critical moment during injury or disease, or generally throughout our lives – we do better. We feel less pain, less fatigue, less sickness. Our immune system works with us instead of against us. Our bodies ease off on emergency defences and can focus on repair and growth.

A lot of what I do are procedures prescribed for the psychological benefit of the patient which then instigates a physiological effect. I am there to work with optimism, a belief in healing, and imagining - which all work to create optimal conditions for health via the nervous system and the endocrine system.

Norman Doidge considers the concerns of those who say therapists that focus on possibilities of healing may be raising false hope. He writes: To those who only worry about raising false hope, I say, I wish that false hope was all we had to worry about… We must also worry about false despair, a problem with no name… The harm done by false hope is familiar, serious, but often transient, for when it comes to brain problems, if the treatment is ineffective, the patient is quickly brought back to cruel reality. But if the patient has a condition that might have been helped by one of those novel approaches, the damage caused by a clinician mistakenly telling a person nothing can be done risks condemning that person to a permanent loss of what would have been a fuller life.