Negative Rainfall Shocks Increase Levels of the Stress Hormone Cortisol Among Poor Farmers in Kenya

Does poverty lead to stress? Despite several studies showing correlations between socioeconomic status and levels of the stress hormone cortisol, it remains unknown whether this relationship is causal. We used random weather shocks in Kenya to address this question. Our identification strategy exploits the fact that rainfall is an important input for farmers, but not for non-farmers such as urban artisans. We obtained salivary cortisol samples from poor rural farmers in Kianyaga district, Kenya, and informal metal workers in Nairobi, Kenya, together with GPS coordinates for household location and high-resolution infrared satellite imagery measuring rainfall. We show that the absence of rain constitutes a random negative income shock for farmers, but not for non-farmers. We find that low levels of rain in the preceding year increase cortisol levels among farmers, but not non-farmers. Similarly, farmers but not non-farmers exhibit higher levels of self-reported stress when the preceding year had high compared to low levels of rain. In addition, the effect of rain on cortisol is larger in farmers who depend solely on agriculture for their income than among those who also have other sources of income. Together, these findings suggest a causal effect of negative shocks on stress levels.