Of the many factors that influence stress responses in young people, s
tage of development has a place of particular importance. This is not
a one-way street, however, because stressors also affect levels of dev
elopment. This article explores certain aspects of this reciprocal rel
ationship. For purposes here, we use the term stressor to include anyt
hing that is stressful, and do not differentiate trauma, deprivation,
or loss. We examine several Lines of development and their use in unde
rstanding, predicting, and, by extension, treating both internal stres
s and external responses.