What happens to health during an economic recession? The question surely is a no-brainier. Wages drift down, unemployment goes up. Those who have lost jobs become depressed; those who haven’t grow fearful and anxious that they may. The outcome for many is stress if not deprivation. Health, it’s clear, will suffer; the death rate is bound to rise. Right?

Wrong – at least if the experience of history, and one bit of history in particular, is anything to go by. Few economic downturns have been as dramatic and as deep as the Great Depression that overtook America during the 1930s. But figures from that time show that mortality fell and life expectancy increased. The data suggest that economic hardship is good for health. Can this be true?

Links between bodily and economic well-being are far from straightforward. In the related area of socioeconomic inequality we’ve already become aware of unexpected influences through the work of Professor Richard Wilkinson of the University of Nottingham.

In his 2009 book The Spirit Level, co-authored with Kate Pickett, he summarised a raft of research all pointing in more or less the same direction. In countries where there is a big earnings gap between rich and poor, life expectancy is lower while mental illness, obesity and drug and alcohol abuse are all more common.

The real surprise is that it’s not only the poor who suffer. The population as a whole do less well if the gap is wider. The nations with the smallest wealth gap and the lowest incidence of health and social problems are the Japanese and the Scandinavians. The countries with, respectively, the greatest and highest are America, Portugal and Britain. The biological explanation for this is uncertain, but possibly mediated by the hormonal effects of perpetual anxiety about status and position, or loss of them. Economics affects health but not always as you might expect.

Dr Jose Tapia Granados is a researcher with a particular interest in the Great Depression.A doctor by training, he moved into economics and works at the Institute for Social Research at the University of Michigan. During the Depression, from mid 1929 through to 1933, he says, life expectancy at birth rose from 57.1 to 63.3 years; mortality fell. The pattern was much the same for men and women, and blacks and whites.

Years of recession are followed by years of recovery in which GDP returns to what it was and then grows. Between 1934 and 1936 the US economy boomed – but mortality rose and life expectancy fell. In 1938, there was another recession and another reversal of the trends. The pattern lasts throughout economic ups and downs from the start of the 1920s to the end of the 1940s. Deaths from TB and cardiovascular disease tended to fall in bad years, but peaked in economic expansions.

This apparently perverse relationship between changes in economic activity and changes in mortality was first seen as far back as the 1920s – to the bewilderment of those who’d noticed it. “They were so puzzled they felt they must be doing something wrong with the numbers,” says Dr Tapia Granados. More work in the 1970s fostered the suggestion that although the figures were right they reflected a lag between the downturns and the emergence of their damaging effects. Although the effects might appear during the recovery phase, it was said, they were not caused by it.

Dr Tapia Granados doesn’t accept this explanation, saying that for this to be credible, he says, business cycles would have to be regular and of equal length. So what is going on? There is evidence that in periods of economic expansion people smoke and drink more, sleep less, work longer, experience more stress, and suffer more industrial injures – all bad for health.

And what of the period of economic contraction? It’s a mirror image, he says, in which most of these influences are reversed. An enforced switch to part-time working, for example. “To work many hours per day increases risk of heart attack. Fewer hours decreases risk. During recessions road traffic deaths decrease and during expansion they increase.” Hence the counterintuitive outcome; recovery from recession, not the recession itself, does harm.

Critics point to a contradiction between this and the link between rising GDP and improving health. Dr Tapia Granados acknowledges this, but denies a contradiction, saying: “I’m talking about fluctuations on top of the general trend.”