Expectations about pain can affect its intensity

Positive thinking was as powerful as a shot of morphine for relieving pain and reduced activity in parts of the brain that process pain information.

The Wake Forest University researchers say their findings show that by merely expecting pain to be less it will be less.

Their work is published in Proceedings of the National Academy of Sciences.

Positive thinking

Dr Robert Coghill and his team studied 10 normal, healthy volunteers who had a heat simulator applied to their legs while their brains were being scanned using functional magnetic resonance imaging (fMRI).

The heat simulator was used to produce pain and fMRI was used to map brain activity.

The brain can powerfully shape pain Researcher Dr Robert Coghill

Before subjects underwent brain imaging, they learned to expect mild, moderate, or severe painful heat stimuli following different signals. None of the stimuli were hot enough to cause burns or damage the skin.

During brain imaging, a small percentage of the severe stimuli were incorrectly signalled as moderate stimuli to create expectations of decreased pain.

All 10 volunteers reported less pain when they expected lower levels of pain.

These expectations reduced reports of pain by more than 28% - similar to an analgesic dose of the potent painkiller morphine.

At the same time, activity in areas of the brain important to both sensory and emotional processing of pain decreased. These areas included the primary somatosensory cortex, the insular cortex and the anterior cingulate cortex.

More than just pills

Dr Coghill explained: "Pain is not solely the result of signals coming from an injured body region.

"Pain needs to be treated with more than just pills. The brain can powerfully shape pain, and we need to exploit its power."

He said the findings underscored the potential of cognitive therapy for the treatment of pain.

This study goes some way to explaining the positive impact of these psychological techniques in chronic pain states Dr Beverly Collette, president of the British Pain Society

Dr Ed Keogh, a psychologist and pain researcher from the University of Bath, said: "For some time now we have known that psychological factors such as expectations play a role in the perception and experience of pain.

"This work is intriguing as it aims to identify specific brain regions linked to both the pain experience and expectations associated with pain.

"By empirically demonstrating such links, such research adds weight to the notion that how we think can effect what we feel. This is turn may have important implications for the way in which we prepare people for potentially painful events such as going to the dentist, childbirth or an operation."

Dr Beverly Collette, president of the British Pain Society, said: "Most people who work in pain clinics use cognitive therapy to help people manage their pain better.