Childhood and adolescent anxiety and depression: beyond heritability.
OBJECTIVE
To review the methodology of behavior genetics studies addressing research questions that go beyond simple heritability estimation and illustrate these using representative research on childhood and adolescent anxiety and depression.


METHODS
The classic twin design and its extensions may be used to examine age and gender differences in the genetic determinants of complex traits and disorders, the role of genetic factors in explaining comorbidity, the interaction of genes and the environment, and the effect of social interaction among family members. An overview of the methods typically employed to address such questions is illustrated by a review of 34 recent studies on childhood anxiety and depression.


RESULTS
The review provides relatively consistent evidence for small to negligible sex differences in the genetic etiology of childhood anxiety and depression, a substantial role of genetic factors in accounting for the temporal stability of these disorders, a partly genetic basis of the comorbidity between anxiety and depression, a possible role of the interaction between genotype and the environment in affecting liability to these disorders, a role of genotype-environment correlation, and a minor, if any, etiological role of sibling interaction.


CONCLUSIONS
The results clearly demonstrate a role for genetic factors in the etiology and temporal stability of individual differences in childhood anxiety and depression. Clinical implications of the findings are discussed.
Franić
Sanja
S
Vrije Universiteit Amsterdam, Faculty of Psychology and Education, Department of Biological Psychology, Van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands. SF.Franic@psy.vu.nl
Middeldorp
Christel M
CM
Dolan
Conor V
CV
Ligthart
Lannie
L
Boomsma
Dorret I
DI
D000293:Adolescent; D001008:Anxiety Disorders / Q000235:genetics* / Q000523:psychology*; D002648:Child; D015897:Comorbidity; D003866:Depressive Disorder / Q000235:genetics* / Q000523:psychology*; D004200:Diseases in Twins / Q000235:genetics* / Q000523:psychology*; D044127:Epigenesis, Genetic / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics* / Q000523:psychology*; D005838:Genotype; D006801:Humans; D008297:Male; D012307:Risk Factors; D012737:Sex Factors; D012931:Social Environment; D018433:Twin Studies as Topic