Reduced Functional Status and Social Conflict Increase Risk of Depression in Adulthood among Modernizing Amazonian Forager-Farmers

Jonathan Stieglitz, University of New Mexico
Michael D. Gurven, University of California, Santa Barbara
Eric Schniter, Chapman University
Christopher von Rueden, University of California, Santa Barbara
Hillard S. Kaplan, University of New Mexico

Pre-modern societies are under-represented in studies of well-being. This paper tests an evolutionary framework regarding mood variation, in the continuum from well-being to depression. We propose that mood variation responds to two fitness-related features of life: 1) economic productivity as it is affected by functional status; and 2) social standing. We test predictions derived from this framework among Bolivian forager-farmers. Results show a strong positive relationship between functional status and well-being after controlling for age, gender, social conflict, and market involvement. Depression is associated with social conflict, but only among non-kin. The Tsimane age profile of well-being is not characterized by a “mid-life crisis”; depression increases with age, as functional status declines. While modernization is marginally associated with depression, market access is associated with lower depression scores later in life. Depression appears to be a response to conditions experienced over human history, and not simply a byproduct of modern environments.