[Psychiatric disorders of environmental outpatients--results of the standardized psychiatric interview (CIDI) from the German multi-center study on Multiple Chemical Sensitivity (MCS)].

Background: A nationwide, environmental outpatient-based multi-center two-phase study on Multiple Chemical Sensitivity (MCS) was conducted from 1999 until 2004. The aim of the study was to characterize more precisely the health-complaints relevant for the MCS-phenomenon. A standardized psychiatric interview (CIDI), used to identify frequency, character and duration of psychiatric disorders and their chronological relation to the environment-related health complaints of the patients, formed part of the extensive diagnostic procedure.

Method: 251 (86.3%) of the 291 attendees of the environmental outpatient departments in Aachen, Berlin, Bredstedt, Freiburg, Giessen and Munich, were examined using the German version (M-CIDI/DIA-X) of the Composite International Diagnostic Interview.

Results: 83.7% (lifetime prevalence rate) fulfilled the diagnostic criteria of at least one psychiatric disorder, with the 12-month and 4-week prevalence rates being 76.5% and 64.5%, respectively. Environmental outpatients, in all prevalence periods, had significantly higher rates of psychiatric disorders than the comparable general population. Somatoform disorders were most frequently diagnosed, followed by depressive and phobic disorders. For 81.2% of the patients the psychiatric disorder started long before the environment-related health complaints (average 17 years).

Conclusions: This study confirms the results of earlier studies, i.e. that patients with environment-related health complaints suffer from psychiatric disorders more frequently than the general population. The high environmental outpatients really suffer from psychosomatic complaints, but attribute the causes to the environment. Application of specific therapeutic regimen is recommended for those patients, whose psychiatric disorders are safeguarded diagnostically and for whom a relevant exposure is unlikely.