Dry eye disease (DED) is highly prevalent among individuals with diagnosed psychiatric disorders, according to new research using nationwide data across Taiwan from 1997 to 2011.

The study shows that patients with DED had a significantly greater likelihood of having dementia, bipolar disorder, depression and neurotic disorders. Further analyses revealed that patients with psychiatric conditions such as schizophrenia, bipolar disorder, clinical depression and neurotic disorders were likely to develop dry eye. Of the 75,650 records of patients with psychiatric disorders reviewed, 3,665 developed dry eye—a prevalence of 4.84%. Within the study, female sex, older age and a number of medical comorbidities were associated with higher risk of DED.

The researchers offered three hypotheses for the connection. One was that inflammation may play a key role in the pathogenesis of both depression—and perhaps other psychiatric disorders—and DED. In patients with DED, increased production of inflammatory cytokines was found in the tears and conjunctiva. Additionally, research shows patients with depression had high levels of the same inflammatory cytokines and neuropeptides in the blood.

A second idea suggests that some of these patients have a lower threshold of pain perception and often complain of worse DED as a result. The team considered that selective serotonin reuptake inhibitors (SSRIs), a class of antidepressant drugs, may actually cause an anticholinergic side effect whereby altered serotonin levels affect the sensitivity thresholds of corneal nerves.