The authors of the new study warned that a research strategy that tries to tie genes with environmental factors may be fraught with danger, but that scientists should be looking at both environmental and genetic factors in trying to account for mental illness.
"We have to work in both directions," Merikangas said.
The U.S. National Institute of Mental Health has more on depression.
SOURCES: Kathleen Ries Merikangas, Ph.D., senior investigator and chief, genetic epidemiology research branch, U.S. National Institute of Mental Health Intramural Research Program; Keith A. Young, Ph.D., vice chair, research, Texas A&M Health Science Center College of Medicine Department of Psychiatry and Behavioral Science, and neuroimaging and genetics core leader, VA Center of Excellence for Research on Returning War Veterans, Central Texas Veterans Health Care System; June 17, 2009, Journal of the American Medical Association