Purpose: The experiences, skills, and internal resources that informal caregivers bring into their role may play a critical part in their mental health and well-being. This study examined how caregiver internal resources changed over a 10 year period, and how this was related to caregivers' well-being.; Methods: Data are from the Midlife in the United States (MIDUS) study, a national sample of adults, at two time points: 1995-1996 (T1) and 2004-2006 (T2).