Lyme borreliosis and associations with mental disorders and suicidal behavior: a Danish nationwide cohort study


Lyme borreliosis is a tick-borne infectious disease that may confer an increased risk of mental disorders, but previous studies have been hampered by methodological limitations, including small sample sizes. The authors used a nationwide retrospective cohort study design to examine rates of mental disorders after Lyme borreliosis.

Methods :

Using Denmark’s National Patient Register and Central Psychiatric Research Register, and including all people living in Denmark from 1994 to 2016 (N=6,945,837), the authors assessed the risk of mental disorders and suicidal behaviors in all people diagnosed with Lyme borreliosis in hospitalized patients and outpatient hospital contacts (N = 12,156). Incidence rate ratios (IRR) were calculated by Poisson regression analyses.


People with Lyme borreliosis had higher rates of any mental disorder (IRR = 1.28, 95% CI = 1.20, 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 death by suicide (IRR = 1.75, 95% CI % = 1.18, 2.58) compared to those without Lyme borreliosis. The 6-month interval after diagnosis was associated with the highest rate of all mental disorders (IRR = 1.96, 95% CI = 1.53, 2.52), and the first 3 years after diagnosis were associated with the highest suicide rate (IRR = 2.41, 95% CI = 1.25, 4.62). Having more than one episode of Lyme borreliosis was associated with increased incidence rates for mental disorders, emotional disorders, and suicide attempts, but not for suicide deaths.


People diagnosed with Lyme borreliosis in a hospital setting had an increased risk of mental disorders, emotional disorders, suicide attempts, and suicide. Although the absolute risk to the population is low, clinicians should be aware of the potential psychiatric sequelae of this global disease.