SCIENTISTS say that the loneliness of a long-distance runner is real and does have an effect.

In rats, running normally has many beneficial effects, including the generation of new brain cells, scientists led by Elizabeth Gould at Princeton University say in Nature Neuroscience, but when the animals run alone no such cells are generated. The results indicate that loneliness can turn a normally beneficial activity into a damaging one — at least in rats.

Running is a natural activity for rats, and one they enjoy, Dr Gould’s team says. Even rats raised in a laboratory will run on a wheel without being bribed with food, but when the activity is withdrawn rats that are used to running suffer physiological and psychological “withdrawal symptoms”.

Experiments suggest that the context in which the activity is carried out is also important.

The rats were raised together, but a week before the experiment was carried out some were moved to individual cages. They were then allowed to exercise either alone or in company, and the effects on their brains were studied.

The team concluded that the solitary rats had higher levels of the stress hormone corticosterone when exposed to stress.

While running — a stressful activity — corticosterone was raised in all the rats, but only in the solitary rats was its effect to reduce brain cell creation.

The findings suggest that stress can affect even activities that are normally beneficial and that, for social animals, the stress of being alone is considerable.

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