Millions of people are now suffering from long COVID, which presents with a staggering array of possible symptoms that can linger for months, or even years. To provide more answers to this frustratingly relentless condition, researchers have tested an association between mental stresses and long COVID.

These stressors include depression, anxiety, and types of distress usually overlooked, including loneliness, perceived stress, and specific worry about COVID.

Surprisingly, these stressors were a stronger predictor of long COVID than physical comorbidities, including a history of hypertension, diabetes, high cholesterol, asthma, and cancer.

Ironically, hearing of these connections can add to anxiety. Still, they are an essential and timely reminder that we must prioritize our mental health even amid an ongoing global pandemic. And while the reasons behind these stressors are very different, they can all challenge our bodies in similar ways.

"There's a long history of people not taking these [mental health] conditions as seriously as they might take physical health conditions that might be easier to measure or easier to see," Harvard University neuroepidemiologist Andrea Roberts told StatNews.

"For long COVID, obviously, then, it becomes very important to look at psychological health, and it raises more broadly the question of the importance of identifying and treating mental health issues."

The team is emphatic that this in no way means long COVID symptoms are all in our head – listing several reasons why the chronic condition is not psychosomatic.

Roberts, Harvard medical doctor Siwen Wang, and their colleagues based their analysis on 54,960 participants of large ongoing nurses' health studies. Of those, the researchers collected data from 3,193 nurses who ended up having COVID. The volunteers filled out baseline, then follow-up questionnaires over 19 months starting from April 2020.

The researchers found long COVID was between 30-50 percent more likely for those who had symptoms of any of the considered stressors.

"Participants who experienced high levels of two or more types of distress [had] nearly 50 percent greater risk of post- COVID-19 conditions than those who did not experience a high level of distress," Wang and team write in their paper.

More than 40 percent of those who developed long COVID had no previous mental health conditions. The study's results remained similar when they excluded participants reporting psychiatric, cognitive, and neurological symptoms.

"We were surprised by how strongly psychological distress before a COVID-19 infection was associated with an increased risk of long COVID," says Wang.

"Distress was more strongly associated with developing long COVID than physical health risk factors such as obesity, asthma, and hypertension."

Most other long COVID symptoms, like coughing, are not symptoms associated with mental illness. What's more, while physical activity is well established as protective against mental illness relapses, half of those with long COVID experienced relapses when trying to exercise; physical and mental health stressors that could exacerbate long COVID need to be considered in tandem.

Psychological stress has been linked to inflammation through the release of inflammatory cytokine proteins, which have also been implicated in long COVID. Studies suggest stress also suppresses our immune system.

Although the study is large, most participants were of a similar demographic – mostly white women with an average age of around 50. Also, the researchers have still just established an association and not a clear link that this combination causes long COVID.

It may be something that's common to these types of distress, rather than the mental health conditions themselves, that is playing a role in long COVID.

However, this isn't the first study to suggest the association between distress and long COVID. A UK study involving multiple sclerosis patients found that almost 30 percent experienced prolonged COVID symptoms for at least 4 weeks, and another 12 percent experienced them for at least 12 weeks.

Wang and the team also highlight how other researchers found similar links between mental illness and long-term symptoms after Lyme disease or CFS/ME.

More work is needed to understand the whole picture, but investigating such potential leads could help researchers determine what exactly is going on with this chronic condition that more and more people are facing every day.

"These results also reinforce the need to increase public awareness of the importance of mental health and to get mental health care for people who need it, including increasing the supply of mental health clinicians and improving access to care," concludes Roberts.

This research was published in JAMA Psychiatry.