Study of the Week: Can Lyme Disease Increase the Risk of Psychiatric Disorders?

Welcome to Study of the Week from Patient Worthy. In this segment, we select a study we posted about from the previous week that we think is of particular interest or importance and go more in-depth. In this story we will talk about the details of the study and explain why it’s important, who will be impacted, and more.

If you read our short form research stories and find yourself wanting to learn more, you’ve come to the right place.


This week’s study is…

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

We previously published about this research in a story titled “Lyme Disease Linked to Increased Psychiatric Disorder Risk” which can be found here. The study was originally published in the scientific journal The American Journal of Psychiatry. You can view the abstract of the study here.

This research team was affiliated with the Copenhagen University Hospital and Columbia University.

What Happened?

We’re around mid-to-late summer now, and these warm days are times of peak activity for disease-carrying parasites such as mosquitoes and ticks. Ticks can carry many diseases but in the US they are probably most noted for transmitting Lyme disease. Prior research has suggested that contracting the disease can increase the risk of psychiatric problems, such as thoughts of suicide and depression. However, these findings are based on small, limited studies. The goal of this research was to attempt to find the correlation on a much larger scale.

In this study, a retrospective nationwide cohort from the country of Denmark was used in order to evaluate the rate of mental disorders in people who had been infected with Lyme disease. This data was evaluated from a 22 year period (1994-2016) and included seven million people. The researchers also took into account potential variables such as socioeconomic factors, age, comorbidities, and sex, which could also have an impact on rates of mental illness. The data drew from people that had been diagnosed with the illness in the hospital setting.

The findings from this study were quite decisive. People infected with Lyme disease had higher rates of mental disorder in general; in fact, the risk of mental disorder of any kind in these patients was 24 percent higher than in those who hadn’t had the disease. The risk of affective disorders (mental illness affecting mood), death by suicide, and suicidal thoughts were also higher in Lyme disease patients. The risk of suicide was 75 percent higher. In patients from ages 20-29, the risk of mental illness was the highest. In people that had been infected twice or more, the risk of mental illness increased by 79 percent.

About Lyme Disease

Lyme disease is an infectious disease caused by bacteria of the genus Borrelia. This bacteria is commonly spread to humans through the bite of a tick. In the US, the species of tick associated with Lyme disease is called the deer tick or the black-legged tick (Ixodes scapularis). A tick must be attached to a person for at least 36 hours to transmit the bacteria. Symptoms of this disease include a distinctive bullseye rash surrounding the bite, fatigue, malaise, headache, and fever. Delays in treatment can lead to more serious symptoms, such as facial paralysis, mood changes, memory loss, sleeping difficulties, meningitis, arthritis, and others. In most cases, prompt treatment can effectively cure the infection. Delayed treatment increases the chance of serious complications and long-term, lingering symptoms. The number of cases of the disease appears to be growing annually. To learn more about Lyme disease, click here.

Why Does it Matter?

While past research had already suggested that there was a link between Lyme disease and an increased risk of mental illness, the findings from this study are the first that have truly demonstrated the connection on a mass scale. Lyme disease, while certainly treatable, is not a particularly well-understood disease; difficulties such as well-documented instances of patients experiencing long-term signs and symptoms following treatment (‘post-treatment Lyme disease syndrome) could also play a role in the increased risk of mental disorder.

“Treating clinicians and patients should be aware of an increased risk of mental health problems, particularly the first year after a severe Lyme disease infection, and if mental health issues arise, patients should seek relevant treatment and guidance.” – Dr. Michael Eriksen Benros, Lead Investigator, Copenhagen University

Of special note is the risk of suicide, which is higher than the risk of mental disorders alone. In the future, the treatment of Lyme disease should take into account these unusual risks that do not occur in most infections, and mental health support should be a part of the treatment conversation between patient and physician from the start. Hopefully, this support can lead to improvements in mental health outcomes for people that are affected by Lyme disease. 

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