Catch a cold when you're stressed and your mental performance will suffer

July 7, 2000

But the answer could lie in a simple cup of coffee

The common cold might be classified as a minor illness, but its effects can have a serious impact on quality of life, on the health services and in absence from work. It is not just the blocked-up nose and the sore throat; your brain feels sluggish too.

Surprisingly, there had been little research into the psychology of colds before the mid-1980s. But recently knowledge has increased.

My research has involved two main themes. The first is investigating the link between people's psychological state, such as how stressed they feel, and their susceptibility to, and the severity of, colds. Second was to investigate what impact infection and illness have on mental performance, which has important practical implications, especially if skills such as driving are impaired.

Colds are ideal for these types of study in that they are frequent, widespread and can be experimentally induced. After 15 years of research, a coherent picture has emerged.

Previous studies have suggested an association between stress and colds. But much of this research had methodological problems. Also, it was unclear whether stress influenced susceptibility to infection or made a person more likely to report symptoms.

Similarly, the pathways linking stress and illness had not been examined in detail. For example, it was unclear whether stress had a direct effect on the immune system or whether it influenced health-related behaviours such as smoking or drinking, which could then produce an effect.

Many of these problems were overcome at the Medical Research Council's Common Cold Unit before it closed by studying volunteers with experimentally induced infections. The results showed a linear increase in the incidence of colds with stress. This effect was observed across a range of different viruses and was found to be due to stress altering susceptibility to infection and not the development of symptoms following infection.

More recent studies of naturally occurring illnesses have confirmed the stress-illness association and shown that health-related behaviours, such as eating breakfast, can be beneficial. Research has also been extended to study patients who often develop more serious problems when they get a cold, such as worsening asthma, and those with particularly high levels of stress, such as those with chronic fatigue syndrome. All these areas have confirmed associations between stress and susceptibility.

My research has shown that experimentally induced colds and influenza have specific effects on mental performance. Influenza impairs tasks where it is not known when or where a target stimulus will appear, whereas colds lead to slower reaction times and poor hand-eye coordination.

The effects of colds and influenza are not only seen when a person has obvious symptoms of infection, but have also been observed in the incubation period and in convalescence. Similar impairments are seen with naturally occurring colds and influenza.

Furthermore, these illnesses increase susceptibility to the effects of other factors such as noise, alcohol and fatigue. Simulations of real-life tasks also suggest colds may reduce our ability to perform them safely.

Fortunately there is good news for coffee drinkers. It seems caffeine can reduce the adverse effects on performance of having a cold. This could have important implications for developing cold medications that not only relieve the physical symptoms but remove the behavioural malaise as well.

Andrew Smith is director of the centre for occupational and health psychology, school of psychology, University of Cardiff.

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