A few weeks into the COVID-19 pandemic, Danielle Weitzer began noticing that a handful of patients at Jefferson Cherry Hill Hospital who tested positive for the coronavirus were showing psychiatric symptoms, like sudden changes in behavior or personality, agitation, confusion, and delirium.

Weitzer, a psychiatry resident at the Rowan University School of Osteopathic Medicine, said psychiatric symptoms generally come on gradually. But with COVID-19 patients the symptoms are "very acute, and can become very severe in a matter of days,” she said.

Scientists and researchers all over the world are scrambling to uncover more information about the coronavirus as the number of global cases climbs over three million. While the Centers for Disease Control and Prevention (CDC) has recently updated its list of possible COVID-19 symptoms to include chills, headache, and a sore throat, health officials have not yet included psychiatric symptoms.

Physicians now know that the virus affects the nervous system, said Joseph R. Berger, a professor of neurology at the Hospital of the University of Pennsylvania. This can cause complications in the brain for a small number of people. But he said there may be a simpler explanation for the majority of psychiatric symptoms among COVID-19 patients — a lack of oxygen in the brain due to low levels in the blood, a dangerous condition called hypoxemia. (Hypoxemia can cause hypoxia, when organs are deprived of oxygen.)

“The brain ... cannot withstand low levels of oxygen,” Berger said. “When the brain is not getting enough oxygen, the patient suffers from hypoxia, which can change the way they think.”

Memory loss, difficulty paying attention, and confusion can be signs of poor oxygen supply to the brain, Berger said. And sometimes, those signs can appear before the better-known physical symptoms of COVID-19, a phenomenon that doctors have dubbed “silent hypoxia,” when pneumonia caused by the virus leads to a form of hard-to-detect oxygen deprivation.

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A study of 214 COVID-19 patients in China published in JAMA Network Open last month found that 36.4% experienced neurologic symptoms, which were broadly classified as dizziness, headache, impaired consciousness, and impairments to taste, smell, and vision. The researchers said that patients with severe infections experienced more acute neurologic symptoms.

Berger said that physicians saw similar symptoms during the 2003 SARS outbreak and the 2012 MERS outbreak, which both caused respiratory infections.

“This virus, although chiefly a disease that attacks the lungs, can affect people in ways that might not suggest lung disease initially,” Berger said. “The loss of sense of taste, smell, or peculiar behaviors may tie back to the lungs being affected, so people have to be alert to the possibility that something unusual may be the consequence of COVID-19.”

Weitzer said that at Jefferson, neurologic symptoms are most commonly seen in older patients. She also noted that symptoms are more severe in people with underlying conditions, such as diabetes or asthma.

The symptoms, if caught in time, are not permanent. “Symptoms do improve for people who recover from COVID-19, but it does take a bit,” Weitzer said.

Kevin Caputo, chair of psychiatry at Crozer-Keystone Health System, said it’s not uncommon to see signs of depression or delirium in elderly patients suffering from pneumonia and other illnesses.

“Geriatric patients are more fragile medically, so any illness can accentuate pre-morbid personality traits,” he said. “For example, if I’m stingy in my 20s and 30s, and experience a psychiatric illness in my 70s, I may appear even more like a miser and act like I’m really afraid of people taking my money.”

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Caputo noted that every patient reacts to the infection differently, which is why it’s important to look for a decrease in mental sharpness and focus, loss of memory, difficulties with words, motor and cognitive deficits as well as the more familiar, flu-like symptoms.

“The basic message,” Caputo said, "is that all physicians should be vigilant.”