Dalya Rosner

Is Mountaineering Addictive (and hence down to dopamine ?)

On May 29, 1953, Tenzing Norgay and Edmund Hillary took the last few decisive steps up Mount Everest, and became the first known humans to reach the summit of the highest mountain on Earth. For fifty years their story has captured the popular imagination, and inspired generations of mountaineers, adventurers and ordinary people looking to applaud the stamina of man and marvel at his determination. But over this time, scientists have begun deconstructing why a person might take themselves out of their ordinary environment and perform such a feat.

The golden anniversary of that first successful ascent

is upon us, so let's sit back in our warm comfortable homes away

from the wilds of the Himalayas and examine some of the neurological

events that motivate the human spirit.

Mountain climbing is but one of the many extreme sports branded

by the more cautious amongst us as reckless behaviour. As time goes

by, and technologies evolve, the risk becomes more calculated, but

there are still many dangers on an Everest expedition over which

climbers have little control, and nature can still easily outwit

the physiology of even the best equipped adventurers. Bad weather

conditions, for example, can cause frostbite, whilst the decreased

barometric pressures high up on Everest can lead to altitude sickness.

There are also emotional difficulties to contend with including

homesickness, fear, and the mental torment of being uncertain whether

your credit card bill has been paid on time (note, this was not

a plug for egg.com, for those who have seen the TV advertisement)

!

Despite all the danger - or perhaps because of it - mountain climbing

and other extreme sports have the admiration of amateurs, and the

addiction of the die-hard. Behavioural geneticists, on the other

hand, prefer you to believe that all the enthusiasm and hype boils

down to a simple case of dopamine biology. Scientists have shown

that genes that control sensitivity of our nerve cells to the neurotransmitter

dopamine, one of the brain's pleasure chemicals, are responsible

for a number of personality traits and psychiatric disorders. When

dopamine is released by neurones in the 'reward centre' of the brain,

it generates a feeling of pleasure and well-being as well as increasing

alertness. The heart takes a beating as well; dopamine increases

pulse rate and cardiac contractility, poising the body for action.

Dopamine and sensations of reward are thought to have evolved to

reinforce the motivation for performance of beneficial activities

such as eating and drinking. For instance, when hunger is satiated,

dopamine is released, helping to promote the pattern of behaviour

that led to this beneficial outcome.

Adventures make a person feel more alive - they provide pleasure

and satisfaction and increase awareness and perceptivity. The finding

that dopamine is released during a new experience, and is responsible

for these sensations, therefore comes as no surprise. Remarkably

though, pain can also cause release of dopamine, so it makes sense

that mountain climbing is an enjoyable activity; the climber experiences

extraordinary terrain and pushes himself physically to the point

of agony. Dopamine is released and everyone has fun!

The average person likes an average amount of novelty in his or

her life. But some people seem to be more adventurous and continuously

pursue diversity, even if their activities involve dangers best

left untested. Individuals like this tend to lag if they are not

constantly stimulated, and they begin to feel inert and depressed.

Several landmark studies found that this 'novelty seeking' personality

type is linked to a gene called D4DR which encodes a dopamine receptor,

a structure found on the surface of nerve cells which enables them

to detect the presence of dopamine. Critically, the length of the

D4DR protein affects how strongly cells react to dopamine. People

with a long version (genetically known as a 'polymorphism') of D4DR

are more sensitive to fluctuations in dopamine levels than the more

common short version. They feel low at levels of dopamine that suffice

to stabilise the mood of the average person, but when dopamine levels

are increased, they sense thrills more intensely than comparatively

staid folk, and it is this 'hit' which leaves them craving new highs.

Indeed, certain drugs such as cocaine work by simulating the action

of dopamine on the brain and so, not surprisingly, research has

it has shown that people with longer versions of the D4DR gene are

more likely to become addicted to drugs, although these findings

are controversial. Presumably, these individuals are 'self-medicating'

to correct for the mood deficit caused by their dopamine sensitivity.

Nonetheless, it is important not to lose sight of the fact that

hard-core drug abusers still tend to come from underprivileged groups,

underlining the impact of the environment upon personality, and

the need for social change.

Edmund Hillary talks about his fascination with adventure as a

young boy in several interviews. He must be no stranger to the effects

of dopamine release. But he also speaks about the amount of planning

and organisation that goes into preparing for a major expedition.

Some scientists would like to explain away the fascination with

extreme sports by blaming it on an aberration of genetics. Yet,

if people with a novelty-seeking personality needed a quick fix

to keep their moods stable, would they really seek out a sport as

drawn out as mountaineering? If their attention span lags, could

they be bothered to plot and plan? Perhaps the answer lies in the

magnificence of the mountains. The adventure of exploring the grandeur

of Nature must endlessly re-new itself whilst the thrill of experiencing

the elements that carve our world must help to maintain interest.

Or perhaps the moment-to-moment strategic decisions, which are needed

to make climbing physically possible, make all the planning worthwhile.

- July 2004

About the Author

Dalya Rosner is a PhD student at Cambridge University