title: Functional Disability and Social Conflict Increase Risk of Depression in Older Adulthood Among Bolivian Forager-Farmers.
abstract: OBJECTIVE
  To present an explanatory framework for depression in older adulthood in a small-scale society. We propose that depression is a consequence of functional disability, which can reduce subsistence productivity and resource transfers within and across generations. Social conflict can also disrupt resource flows and should be associated with depression.
  
  
  METHODS
  To evaluate depression among Tsimane forager-farmers of Bolivia, we developed a reliable interview based on focus groups and a review of validated depression scales. Older adults (mean ± SD age = 62 ± 9, n = 325) were recruited regardless of their health status. Demographic, economic, and medical data were collected during annual censuses and routine medical exams.
  
  
  RESULTS
  Depression is associated with reduced energetic status, greater physical limitations, and reduced subsistence involvement after controlling for potential confounds such as age, sex, number of reported unresolved conflicts, and market involvement. Depression is also associated with greater reported conflict, particularly with non-kin.
  
  
  CONCLUSIONS
  Tsimane depression is associated with disability, reduced subsistence productivity, and interpersonal conflict, all of which can disrupt resource flows. Depression appears to be a response to conditions regularly experienced over human history, and not simply a by-product of modernity.
authors.affiliation: Department of Anthropology, University of New Mexico. jonathan.stieglitz@gmail.com.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Stieglitz
authors.affiliation: Economic Sciences Institute, Chapman University, California.
authors.forename: Eric
authors.initials: E
authors.lastname: Schniter
authors.affiliation: Jepson School of Leadership Studies, University of Richmond, Virginia.
authors.forename: Christopher
authors.initials: C
authors.lastname: von Rueden
authors.affiliation: Department of Anthropology, University of New Mexico. Economic Sciences Institute, Chapman University, California.
authors.forename: Hillard
authors.initials: H
authors.lastname: Kaplan
authors.affiliation: Integrative Anthropological Sciences Unit, University of California-Santa Barbara.
authors.forename: Michael
authors.initials: M
authors.lastname: Gurven
mesh_terms: D000203:Activities of Daily Living; D001838:Bolivia / Q000453:epidemiology; D003220:Conflict, Psychological; D003430:Cross-Sectional Studies; D003863:Depression / Q000453:epidemiology*; D006233:Persons with Disabilities; D000067565:Farmers; D005260:Female; D006801:Humans; D007199:Indians, South American; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment; D012940:Social Problems
keywords: Conflict; Depression; Disability; Evolution; Tsimane; Well-being