Facets of neuroticism and musculoskeletal symptoms. A study of middle-aged twins

Olav Vassend, Benedicte Humborstad Orvik, Nikolai Olavi Czajkowski, Espen Røysamb

Abstract


Clinical and epidemiological studies have shown that both site-specific and more widespread musculoskeletal
(MS) conditions are linked to anxiety and depression symptoms. However, the nature of this relationship is
poorly understood, particularly in terms of underlying genetic and environmental influences. Furthermore, the
personality trait neuroticism has been shown to be related to common emotional symptoms and somatic
distress as well as to more serious psychiatric and medical disorders. In modern personality theory, the broad
neuroticism domain is conceptualized as consisting of a set of lower-order facets, such as anxiety, hostility,
and depression, which may be differentially related to various health outcome measures. So far, the role of
neuroticism facets as risk factors for MS conditions has not been explored in genetically informative designs.
In the current study, the relationship between MS symptoms and six neuroticism facets was investigated in
bivariate analyses and in regression models including sex, education level, and general health indices as
control variables. Using multivariate twin modeling, genetic and environmental influences on the phenotypes
and the associations among them were determined. The sample consisted of 746 monozygotic (MZ) and 770
dizygotic (DZ) twins in the age group of 50-65 (mean = 57.11 years, SD = 4.5). The results showed that a
single factor accounted for about 50% of the overall variance in MS symptom reporting. Two neuroticism
facets, N1: anxiety and N3: depression, appeared as significant in the regression analyses. Both these facets
and MS symptoms were strongly influenced by genetic factors [heritability (h2) = 0.46-0.54]. While there was
a considerable overlap in genetic risk factors between the three phenotypes, a large proportion (71%) of the
genetic variance in MS symptoms was unique to the phenotype, and not shared with the neuroticism facets.

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DOI: http://dx.doi.org/10.5324/nje.v26i1-2.2015

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