Vol 5 n° 2 - Psychiatric disorders in somatic medicine
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t  is  increasingly  becoming  recognized  that somatic and psychiatric disorders frequently cooccur in the same individual and that persons with mental illness or a history of it have more medical conditions during their lifetime than the general population.1 Somatic com- plaints involving various types of pain, such as headache, stomach pain, vague, poorly localized pain, and back pain, are frequent in various psychiatric conditions, but the rela- tionship between them and the question of whether psy- choactive drugs similarly improve both conditions have never been clarified. The  mechanisms  for  these  interactions  are  largely unknown, but a variety of indirect and direct mechanisms, which could also be either concomitants or consequences of one condition, have been proposed.The importance of biological vulnerability factors and environment has been heavily debated, and it was proposed that a substantial proportion of morbidity may be attributed not to a spe- cific risk for one disorder, but to few underlying liability factors that are applicable to both somatic and psychiatric disorders.1 Thus, even if psychiatric and somatic conditions do not affect each other, they might still cosegregate if they share common underlying factors, including genetic factors. Especially in complex disorders with multifactor- ial pathophysiological mechanisms, the relevance of genes has  exceeded  the  simple  identification  of  a  disease- enabling cause and is now focusing on importance for treatment response, side effects, interactions with the envi- ronment, and personality factors. It was further proposed that both the vulnerability for different disorders and the individual’s interaction with the environment are influ- enced by genes (“nature and nurture”).2 B a s i c   r e s e a r c h 1 2 9 Common genetic risk factors for psychiatric and somatic disorders Brigitta Bondy, MD I Keywords: gene; polymorphism; fibromyalgia; migraine; cardiovascular disorder; psychiatric disorder Author  affiliations:  Psychiatric  Clinic  of  University  Munich,  Department  of Neurochemistry, Munich, Germany Address  for  correspondence:  Prof  Dr  Brigitta  Bondy,  Psychiatric  Clinic  of University  Munich,  Department  of  Neurochemistry,  Nußbaumstraße  7, D-80336 Munich, Germany (e-mail: Brigitta.Bondy@psy.med.uni-muenchen.de) There is increasing knowledge about considerable comor- bidity between psychiatric and somatic diseases, ques- tioning whether variations in genes could be predispos- ing  factors  for  both  conditions.  With  respect  to  the multiple interactions between brain and body, investiga- tions have centered on variants in several candidate genes for proteins that mediate these interactions and therefore also have implications in psychiatric disorders. The avail- able data, although still preliminary and rare, indicate the importance of polymorphic variants in genes coding for the serotonin (5-hydroxytryptamine, 5-HT) transporter (5-HTT), the 5-HT2A receptor, proinflammatory cytokines, and   the   angiotensin-converting   enzyme   (ACE)   in migraine, fibromyalgia, cardiovascular disorders, and psy- chiatric conditions. The role played by these various poly- morphisms remains to be determined, as does whether they are indicative of common pathophysiological mech- anisms or identify a subgroup of patients with somatic dis- orders that are more closely related to psychiatric symp- toms. Nevertheless, they do at least illustrate the potential influence of genetic differences on illness course and treatment outcome, and might be a rational approach to drug development and treatment paradigms. Dialogues Clin Neurosci. 2003;5:129-138.