Reply to The Importance of Negative Comorbidity

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To the Editor: Tabarés-Seisdedos and colleagues highlight that in schizophrenia and other mental disorders, not only is there excess medical comorbidity, but some physical diseases seem to be less frequent (they call this phenomenon “negative comorbidities”). Some of these negative comorbidities are well known, but there is debate about most of them (for review, see Leucht et al1).

For example, although most studies have found a decreased incidence of polyarthritis in schizophrenia patients, an intriguing epidemiologic article2 describes the same phenomenon for nonspecific back pain—a disease without a genetic etiology—thereby suggesting that the lower incidence may just be due to underreporting by people with schizophrenia. Most population-based studies indeed have reported a decreased incidence of lung cancer in people with schizophrenia compared to the general population. However, there is considerable variability, and the largest study reports an increased incidence,3 although Catts et al4 have explained this finding by pointing to different baseline risks in the different countries.

Overall, there is clearly more “positive comorbidity” than “negative comorbidity,” but we commend Tabarés-Seisdedos and colleagues’ effort to highlight the latter, because more research on this topic may well provide key insights toward understanding mental disorders.

References

1. Leucht S, Burkard T, Henderson J, et al. Physical illness and schizophrenia: a review of the literature. Acta Psychiatr Scand. 2007;116(5):317-333. PubMed doi:10.1111/j.1600-0447.2007.01095.x

2. Mors O, Mortensen PB, Ewald H. A population-based register study of the association between schizophrenia and rheumatoid arthritis. Schizophr Res. 1999;40:67-74. PubMed doi:10.1016/S0920-9964(99)00030-4

3. Lichtermann D, Ekelund J, Pukkala E, et al. Incidence of cancer among persons with schizophrenia and their relatives. Arch Gen Psychiatry. 2001;58:573-578. PubMed doi:10.1001/archpsyc.58.6.573

4. Catts VS, Catts SV, O’ Toole BI, et al. Cancer incidence in patients with schizophrenia and their first-degree relatives—a meta-analysis. Acta Psychiatr Scand. 2008;117(5):323-336. PubMed doi:10.1111/j.1600-0447.2008.01163.x

Stefan Leucht, MD

W. Wolfgang Fleischhacker, MD

wolfgang.fleischhacker@i-med.ac.at

Author affiliations: Department of Psychiatry and Psychotherapy, Technische Universität München, Munich, Germany (Dr Leucht); and Department of Biological Psychiatry, Medical University Innsbruck, Innsbruck, Austria (Dr Fleischhacker). Financial disclosure: See disclosure statements in original article [2008;69(4):518]. Funding/support: The original article derived from meetings funded by an independent educational grant from Pfizer, Inc.

doi:10.4088/JCP.08lr04991a

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