Eye misalignment may raise risk of mental illness

NEW YORK (Reuters Health) - A study released today suggests that children with "exotropia type" strabismus -- a visual defect in which the eyes are misaligned and turn outward - may be at increased risk for developing mental illness by young adulthood.

However, children with "esotropia type" strabismus, in which the eyes are turned inward, do not appear to be at increased risk for mental illness in early adulthood, according to the study published in the November issue of Pediatrics.

Strabismus is often informally referred to as "cross-eyes." People with the condition may have one or two eyes that turn inward, outward, up or down. The exact cause of such misalignment is not fully clear.

For their study, Dr. Brian G. Mohney and colleagues from Mayo Clinic in Rochester, Minnesota, reviewed the medical records for 407 patients with childhood strabismus and 407 matched control subjects from Olmsted County, Minnesota.

Through follow-up to an average age of 17.4 years, 41.3 percent of strabismus patients and 30.7 percent of controls were diagnosed with a mental illness.

Further analysis showed that children with exotropia type strabismus were 3.1-times more likely to develop a mental illness than their peers without strabismus through an average age of 20.3 years. Children with esotropia type strabismus, as noted, were no more likely than controls to develop mental illness.

"Why exotropia and not esotropia would be associated with the development of mental illness by early adulthood is unclear," Mohney and colleagues admit. "Ocular misalignment would seem to have similar effects on individuals with strabismus regardless of whether it is esotropic or exotropic."

They add that "heredity is a more likely basis for any association between exotropia and mental illness."

SOURCE: Pediatrics November 2008.