A population based family study of symptoms of anxiety and depression: the HUNT study

To estimate an upper limit on the heritability of self-reported symptoms of anxiety and depression in a large and population representative nuclear family sample.

The ten-item symptom checklist (SCL-10) was administered as part of a health survey in a Norwegian county. The SCL-10 is a shortened version of the SCL-25, assessing symptoms of anxiety and depression. In all, 46,064 people responded, and with data from Statistics Norway, responses of first-degree relatives could be linked. Polychoric correlations between family members score on SCL-10 were calculated, and a structural equation model was fitted to these correlations using the software package R.

All correlations between nuclear family members were in the range of 0.12 to 0.16, indicating small but significant familial influences on SCL-10. In the best fitting model, heritability was estimated at 0.25 (95% CI=0.22-0.27), and sibling specific environmental effects could be discarded.

The estimated upper level heritability for SCL-10 in our sample was lower than what has been reported in twin studies of similar measures.