Misaligned eyes in children are associated with an increased prevalence of mental illness, results of a large study suggest.
“Psychiatrists who have a patient with depression or anxiety and notice that patient also has strabismus might think about the link between those two conditions and refer that patient,” study investigator Stacy L. Pineles, MD, professor, department of ophthalmology, University of California, Los Angeles, told this news organization.
University of California at Los Angeles
Dr. Stacy L. Pineles
The study was published online March 10 in JAMA Ophthalmology.
A common condition
Strabismus, a condition in which the eyes don’t line up or are “crossed,” is one of the most common eye diseases in children, with some estimates suggesting it affects more than 1.5 million American youth.
Patients with strabismus have problems making eye contact and are affected socially and functionally, said Dr. Pineles. They’re often met with a negative bias, as shown by children’s responses to pictures of faces with and without strabismus, she said.
There is a signal from previous research suggesting that strabismus is linked to a higher risk of mental illness. However, most of these studies were small and had relatively homogenous populations, said Dr. Pineles.
The new study includes over 12 million children (mean age, 8.0 years) from a private health insurance claims database that represents diverse races and ethnicities as well as geographic regions across the United States.
The sample included 352,636 children with strabismus and 11,652,553 children with no diagnosed eye disease who served as controls. Most participants were White (51.6%), came from a family with an annual household income of $40,000 or more (51.0%), had point-of-service insurance (68.7%), and had at least one comorbid condition (64.5%).
The study evaluated five mental illness diagnoses. These included anxiety disorder, depressive disorder, substance use or addictive disorder, bipolar disorder, and schizophrenia.
Overall, children with strabismus had a higher prevalence of all these illnesses, with the exception of substance use disorder.
After adjusting for age, sex, race and ethnicity, census region, education level of caregiver, family net worth, and presence of at least one comorbid condition, the odds ratios among those with versus without strabismus were: 2.01 (95% confidence interval, 1.99-2.04; P < .001) for anxiety disorder, 1.83 (95% CI, 1.76-1.90; P < .001) for schizophrenia, 1.64 (95% CI, 1.59-1.70; P < .001) for bipolar disorder, and 1.61 (95% CI, 1.59-1.63; P < .001) for depressive disorder.
Substance use disorder had a negative unadjusted association with strabismus, but after adjustment for confounders, the association was not significant (OR, 0.99; 95% CI, 0.97-1.02; P = .48).
Dr. Pineles noted that the study participants, who were all under age 19, may be too young to have substance use disorders.
The results for substance use disorders provided something of an “internal control” and reaffirmed results for the other four conditions, said Dr. Pineles.
“When you do research on such a large database, you’re very likely to find significant associations; the dataset is so large that even very small differences become statistically significant. It was interesting that not everything gave us a positive association.”
Researchers divided the strabismus group into those with esotropia, where the eyes turn inward (52.2%), exotropia, where they turn outward (46.3%), and hypertropia, where one eye wanders upward (12.5%). Investigators found that all three conditions were associated with increased risk of anxiety disorder, depressive disorder, bipolar disorders, and schizophrenia.
Investigators note that rates in the current study were lower than in previous studies, which showed that children with congenital esotropia were 2.6 times more likely to receive a mental health diagnosis, and children with intermittent exotropia were 2.7 times more likely to receive a mental health diagnosis.
“It is probable that our study found a lower risk than these studies, because our study was cross-sectional and claims based, whereas these studies observed the children to early adulthood and were based on medical records,” the investigators note.
It’s impossible to determine from this study how strabismus is connected to mental illness. However, Dr. Pineles believes depression and anxiety might be tied to strabismus via teasing, which affects self-esteem, although genetics could also play a role. For conditions such as schizophrenia, a shared genetic link with strabismus might be more likely, she added.
“Schizophrenia is a pretty severe diagnosis, so just being teased or having poor self-esteem is probably not enough” to develop schizophrenia.
Based on her clinical experience, Dr. Pineles said that realigning the eyes of patients with milder forms of depression or anxiety “definitely anecdotally helps these patients a lot.”
Dr. Pineles and colleagues have another paper in press that examines mental illnesses and other serious eye disorders in children and shows similar findings, she said.