Neuroticism and self-reported somatic health: a twin study

Using a twin sample (N = 188; 53 monozygotic and 39 dizygotic twin pairs, and 4 single twins whose co-twin did not participate), this study sought (1) to estimate heritabilities of neuroticism and of somatic complaints rated on the basis of two different time frames ('the last week' vs. 'in general'); (2) to estimate the genetic association between neuroticism and the complaints indices and (3) to examine to what extent somatic complaints are aetiologically distinct from neuroticism. Using models with common additive genetic (A) and individual-specific environmental (E) factors, the heritabilities for neuroticism and complaints 'in general' and during 'the last week' were 0.46 (0.20-0.65), 0.44 (0.22-0.62), and 0.45 (0.22-0.63), respectively. Nearly 60% of the phenotypic correlation between neuroticism and somatic complaints were accounted for by A. Furthermore, a substantial part of the variance in somatic complaints was due to unique genetic and individual-specific environmental influences unrelated to neuroticism. These results suggest that somatic complaints are moderately heritable and that a considerable portion of the covariance between neuroticism and complaints measures is due to genetic factors. Yet, the findings also suggest that these two attributes are distinct entities with overlapping, but not identical, underlying genetic and environmental influences.