Lyme disease increases risk for mental disorders, suicide

People who received a Lyme disease diagnosis in a hospital setting had increased risk for mental disorders, affective disorders, suicide attempts and suicide, according to results of a nationwide cohort study conducted in Denmark.

“Several [prior] studies were hampered by small sample size, ascertainment bias, lack of an appropriate control group, use of poorly specified or nonstandard criteria for the diagnosis of Lyme borreliosis, reliance on clinical samples, use of unvalidated measures, lack of control for confounding variables or a cross-sectional design,” Brian A. Fallon, MD, MPH, of the department of psychiatry at Columbia University in New York, and colleagues wrote in American Journal of Psychiatry. “Given the methodological limitations of previous studies, the relationship between acute or posttreatment Lyme borreliosis and mental disorders and suicide remains uncertain.”

The researchers conducted a nationwide retrospective cohort study to assess mental disorder rates after Lyme disease diagnosis. They used Denmark’s National Patient Register and the Psychiatric Central Research Register and included data from all 6,945,837 individuals living in Denmark between 1994 and 2016. Using this data, they evaluated the risk for mental disorders and suicidal behaviors among all 12,156 individuals diagnosed with Lyme disease in inpatient and outpatient hospital contacts.

Fallon and colleagues used Poison regression analyses to calculate incidence rate ratios (IRRs).

Results showed higher rates of any mental disorder (IRR = 1.28; 95% CI, 1.2-1.37), affective disorders (IRR = 1.42; 95% CI, 1.27-1.59), suicide attempts (IRR = 2.01; 95% CI, 1.58-2.55) and of death by suicide (IRR = 1.75; 95% CI, 1.18-2.58) among those with vs. without Lyme disease. The researchers noted an association between the 6-month interval after diagnosis and the highest rate of any mental disorder (IRR = 1.96; 95% CI, 1.53-2.52), as well as an association between the first 3 years after diagnosis and the highest rate of suicide (IRR = 2.41; 95% CI, 1.25-4.62). People who had more than one episode of Lyme disease had increased IRRs for mental disorders, affective disorder and suicide attempts, but not for death by suicide.

“Although the absolute population risk is low, clinicians should be aware of potential psychiatric sequelae of this global disease,” Fallon and colleagues wrote.