Functional Somatic Disorders (FSD) and Internalizing Psychiatric Disorders (IPD) are frequently comorbid and likely share familial/genetic risk factors.

We performed a Common Factor Multivariate Analysis of 2 FSDs, Fibromyalgia (FM) and Irritable Bowel Syndrome (IBS), and two IPDs, Major Depression (MD) and Anxiety Disorders (AD), in five kinds of Swedish female–female relative pairs: monozygotic (n = 8,052) dizygotic (n = 7216), full siblings (n = 712,762), half-siblings reared together (n = 23,623), and half-siblings reared apart (n = 53,873). Model fitting was by full information maximum likelihood using OpenMx.

The best-fit model included genetic, shared environmental, and unique environmental factors. The common factor, ~50% heritable with a small shared environmental effect, loaded more strongly on the two IPDs (~0.80) than the 2 FSDs (0.40). Disorder-specific genetic effects were larger for the 2 FSDs (~0.30) than the 2 IPDs (~0.03). Estimated genetic correlations were high for MD and AD (+0.91), moderate between IBS and IPDs (+0.62), and intermediate between FM and MD (+0.54), FM and AD (+0.28), and FM and IBS (+0.38). Shared environmental influences on all disorders were present but small.

In women, FSDs and IPDs shared a moderate proportion of their genetic risk factors, greater for IBS than for FM. However, the genetic sharing between IBS and FM was less than between MD and AD, suggesting that FSDs do not form a highly genetically coherent group of disorders. The shared environment made a modest contribution to the familial aggregation of FSDs and IPDs.

Functional somatic disorders (FSD) characterized by persistent and disabling physical symptoms are common in youth. Diagnostic uncertainty and insufficient illness explanations are proposed as perpetuating factors for FSD and may furthermore serve as barriers for treatment engagement.

The present study is part of a larger randomized trial and aimed at evaluating the impact of systematic assessment and psychoeducation on various clinical outcomes for adolescents suffering from severe FSD.

Ninety-one adolescents (15-19 years) with severe FSD of at least 1 year’s duration were included in the randomized trial AHEAD (Acceptance and Commitment Therapy for Health in Adolescents). All participants received a thorough assessment (approximately 4 hrs.) and a subsequent psychiatric consultation (1.5 hrs) focusing on further psychoeducation and health promoting strategies. Clinical outcomes included self-reported physical health (SF-36), symptom severity, illness perception, illness related behaviour and psychological flexibility. Questionnaires were distributed at baseline (before assessment) and 2 months after randomisation. Data were analysed using simple t-tests.

Assessment and psychiatric consultation were not associated with a clinically relevant improvement of physical health, mean difference 0.23 95% CI [-0.95;1.41] p=0.701. However, a considerate decline was seen on symptom severity (p=0.017), illness worry (p<0.001) and negative illness perceptions (p<0.001). Furthermore, a decline was seen in limiting illness behaviour (p=0.002) and psychological inflexibility (p=0.001).

The results underpin the importance and the potential positive implications of thorough assessment and psychoeducation. Hence, these elements may be in their own right in the systematic and specialised treatment of adolescents with severe FSD.

No significant relationships.