A new study out of Oxford found that one in three people who have survived Covid-19 are diagnosed with a neurological or psychiatric condition within six months of being infected.

The most common mental health conditions were anxiety disorders, mood disorders (such as depression), substance misuse disorders and insomnia. Neurological conditions included things like brain hemorrhage, which is bleeding that interferes with the brain's function; ischemic stroke, which is caused when a vessel supplying blood to the brain is blocked; and dementia.

For the study, researchers looked at patient health records of more than 230,000 people who had confirmed cases of Covid in the United States. They estimated that the likelihood of people being diagnosed with a neurological or mental health disorder following Covid-19 infection was 34%.

The psychiatric conditions were much more common, but the neurological conditions "are significant, especially in those who had severe Covid-19," professor Paul Harrison, lead author of the study from the Department of Psychiatry at Oxford University, said in a release.

So, how does a respiratory disease lead to neurological and psychiatric effects? Here's what you need to know:

How Covid and other viruses affect your brain

In addition to the hallmark symptoms of Covid infection, such as fever, cough and shortness of breath, 25% of people experience symptoms related to their brain and nervous system, including dizziness, headache, debilitating fatigue and "brain fog" or cognitive impairment, which is trouble remembering, learning and concentrating. While symptoms tend to go away once someone recovers, some Covid survivors experience lasting long-term effects.  

At this stage, researchers aren't sure what the exact physiological mechanism is that's driving the neurological and cognitive symptoms. One possible explanation? A study in the New England Journal of Medicine examined brain tissue from people who died from Covid and noticed a combination of inflammation and leaking blood vessels in the brain.

"Covid-19's many neurological symptoms are likely explained by the body's widespread inflammatory response to infection and associated blood vessel injury — not by infection of the brain tissue itself," Dr. Francis Collins, director of the National Institutes of Health, wrote in a blog post on Jan. 14.

Covid also seems to have a stronger effect on people's neurological and mental health than other respiratory conditions: In the new study, there was overall a 44% greater risk of neurological and mental health diagnoses after Covid-19 than after flu, and a 16% greater risk after COVID-19 than with respiratory tract infections.

The mental health effects of having Covid

While most people are dealing with more mental health issues than usual during the pandemic, the anxiety and stress that come with a Covid diagnosis is significant, even for those who recover.

Researchers wrote that the prevalence of mental health conditions among Covid survivors "reflects, at least partly, the psychological and other implications of a Covid-19 diagnosis rather than being a direct manifestation of the illness."

Previous research from the same group at Oxford found that people who were diagnosed with Covid were more likely to be diagnosed with a mental health issue than people coping with other health issues during the pandemic. For example, those recovering from Covid-19 were twice as likely to be diagnosed with a mental health disorder as compared with someone who had the flu.

Almost 20% of Covid patients who recovered were diagnosed with a mental illnesses within three months.

Harrison, the lead author for both studies, said that the findings lay bare the need for mental health services for the large number of people who may be experiencing symptoms.

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