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Chemical intolerance linked with comorbid psychiatric disorders

One in five primary care patients met criteria for chemical intolerance, according to recent study results. The chemically intolerant group reported significantly higher rates of comorbid allergies and more often met screening criteria for a range of possible psychiatric disorders.

“Chemical intolerance is common among low-income, primary-care patients, and should be actively sought, possibly with the aid of an instrument like the [Quick Environmental Exposure and Sensitivity Inventory], especially among patients with a family history of chemical intolerance, a personal history of medication intolerances, or multisystem — including psychiatric — symptoms,” study researcher David A. Katerndahl, MD, MA, told Healio.com.

Katerndahl, a family physician and professor at the Department of Family and Community Medicine at the University of Texas Health Science Center at San Antonio, and colleagues performed a community-based study on the prevalence and clinical characteristics of chemical intolerance in a sample of 400 patients aged 18 years or older who were recruited from two family medicine settings in San Antonio, Texas.

All participants completed a 90-item questionnaire covering demographics, chemical intolerance, mental disorders, functional status and health care use.

Overall, 20.3% of participants met criteria for chemical intolerance and reported significantly higher rates of comorbid allergies, compared with those who were chemically tolerant (53% vs. 40%, respectively; OR=1.67; 95% CI, 1.02-2.72). Participants who were chemically intolerant more often met screening criteria for possible major depressive disorder (OR=11.55; 95% CI, 6.00-22.26), panic disorder (OR=5.97; 95% CI, 3.52-10.11), generalized anxiety disorder (OR=13.16; 95% CI, 7.30-23.73), alcohol abuse disorder (OR=2.39; 95% CI, 1.41-4.06) and somatization disorder (OR=4.90; 95% CI, 2.18-11.01).

Results also showed that the total number of possible mental disorders was linearly related to the prevalence of chemical intolerance. After controlling for demographics, the researchers found that participants with chemical intolerance were significantly more likely to have poorer functional status with increased medical service use (P<.001), including emergency services, total ambulatory care and hospitalizations, compared with those who were chemically tolerant.

The researchers wrote that it is uncommon for primary care clinicians to recognize chemical intolerance in a given patient, and patients are unlikely to report chemical intolerance as their chief complaint.

“Although a detailed discussion of possible biologic mechanisms is beyond the scope of this article, laboratory studies of persons with [multiple chemical sensitivity] or chemical intolerance indicate that both central nervous system sensitization and inflammatory processes contribute to the multisystem clinical picture,” the researchers wrote. “Both sensitization and chronic inflammation also play a role in the medical, psychiatric and substance abuse conditions found at elevated rates in the personal histories, family histories, or both, of patients with [multiple chemical sensitivity].”

Disclosure: The researchers report no relevant financial disclosures.