NEW YORK (Reuters Health, Oct 20) - Research in psychiatrically ill children and adolescents suggests that those with depression, anxiety and other so-called "internalizing" disorders are more likely to have allergies.

Among a sample of 184 young people being evaluated for psychiatric disorders and allergies, 105 (57 percent) had a history of allergic disorders, including asthma, hay fever, hives and eczema.

Psychiatric evaluations revealed that 124 (67 percent) had an internalizing disorder, either alone or in combination with an externalizing disorder, such as ADHD, oppositional defiant disorder and conduct disorder. The children in the sample were between 4 and 20 years old; their average age was 13.

Researchers found that youth with internalizing disorders were almost twice as likely to have a history of allergies than those with a diagnosis that wasn't classified as an internalizing or externalizing disorder. The psychiatric disorders in this group included substance abuse, tic disorders, bed-wetting and attachment disorder.

Moreover, the association was found to be specific for "pure" internalizing disorders. That is, the likelihood of having a history of allergies was significant only among youths who had an internalizing disorder and no other psychiatric conditions.

"These findings add to the growing body of evidence supporting an association between anxiety, depressive, and allergic disorders," write Dr. Mauricio Infante and colleagues from University of Wisconsin, Madison in the Journal of Clinical Psychiatry.

The findings also suggest that these psychiatric and medical disorders "may share risk factors and underlying pathways that contribute to the development of both types of disorders."

The Wisconsin team notes that studies are needed to identify the reasons for these associations so that effective treatment and prevention strategies that target both disorders can be developed.

SOURCE: Journal Clinical Psychiatry, September 2007.