Susceptibility and "Second Hit"
"As daunting as the challenge is, there is nor more compelling reason to attempt to understand the causes of mental illness than these various afflictions exact an enormous human cost. The derangements of thought, emotion, and behavior that characterize mental disorders such as manic-depressive illness, depression schizophrenia, and addiction are agonizing not only for the afflicted individuals but also for their family and friends. The torment of coping with a parent's hallucinations and emotional withdrawal, a sibling's psychotic rage, or a child's self-destructive behavior can exhaust families and leave lasting scars even on those who escape the illness itself. As one woman, who as a child watched both her older brother and her older sister succumb to schizophrenia, said, "They no longer inhabit my present life, but their illnesses haunt me like ghosts.'"
Steven Hyman, M.D., director of the National Institute of Mental Health.
Born to Be Shy?
"As neuroscientists are discovering, the brain is a remarkably adaptable and malleable organ, especially early in life. Even though the research suggests that inherited neurochemistries, whatever they may turn out to be, bias young children to react in particular ways--running away from strange people and strange circumstances or embracing the new with enthusiasm--the child's interactions with family, teachers, and peers can shape that predisposition significantly. Whether some even happens willy-nilly, on purpose, or by accident, we learn and change in response to these interactions, to experiences of caring or abuse, even to the experience of, say, a severe childhood illness. By the time a child is two years old, his or her temperament is already part of a tapestry whose biological and environmental threads are so tightly woven as to be impossible to tease apart."
Jerome Kagan, Ph.D., professor of psychology at Harvard University and co-director of the Mind-Brain-Behavior Initiative at Harvard University.