Objectives
Idiopathic environmental intolerance (IEI) is a disorder characterized by non-specific symptoms attributed to common airborne chemicals. Increasing evidence points to an association between IEI and symptoms of psychological distress. However, whether other risk factors influence this association has not been clarified. The objective of this study was to examine the association between psychological distress and IEI and to determine whether the association is confounded by social support and major life events.

Methods
Data were collected by postal questionnaires; other results from the study have been published previously in this journal. The study included participants from a general population-based study who had reported symptoms of chemical sensitivities (n = 787) and two patient groups. The first patient group (n = 101) included individuals who had contacted the Danish Research Centre for Chemical Sensitivities, and the second included individuals who had been diagnosed with environmental intolerance (n = 136). Multiple, hierarchical linear regression analyses were conducted with four IEI-related domains, i.e., mucosal and CNS symptoms, chemical intolerances and social consequences, as the dependent variables, and psychological distress, social support and major life events as the independent variables.

Results
Our study confirmed positive and statistically significant associations between psychological distress and IEI. The associations remained statistically significant after adjusting for major life events and social support.

Conclusions
The results suggest that the association between IEI and psychological distress cannot be explained by known risk factors. More studies, including longitudinal studies, are needed to determine the role of psychological distress in the development and course of IEI.