Behavioral genetics as a tool for developmental psychology: anxiety and depression in children and adolescents.

Over the past decade there has been a huge increase in the number of behavioral genetic studies looking into anxiety and depression in children and adolescents. There are now enough data in this area to make a review of the results useful. This paper begins with an outline of the methods used in such research and moves on to review the results in extant studies. Overall, these studies indicate modest to moderate genetic influence on both anxiety and depression. However, behavioral genetic methods are also paramount for exploring environmental influences in addition to genetic influences. Shared environment (that which makes family members resemble one another) is rarely identified in adult studies of personality or psychopathology and does not appear to be a significant influence for depression but it is for anxiety. Nonshared environment, which makes family members differ from one another, is found to be a significant influence for both anxiety and depression. Patterns within these results due to rater effects, age effects, sex effects, the precise phenotype measured, and the study design are explored.