1. Department of Sociology, University of Georgia , Athens, Georgia , USA
2. Center for Family Research, University of Georgia , Athens, Georgia , USA
3. Department of Psychology, University of Georgia , Athens, Georgia , USA
4. Department of Psychiatry, University of Iowa School of Medicine , Iowa City, Iowa , USA
5. Department of Epidemiology and Prevention, Wake Forest University, School of Medicine , Winston-Salem, North Carolina , USA