WEDNESDAY, March 10, 2021 (American Heart Association News) -- Grief is a common, if not universal, human experience. But that doesn't make it simple.

It's psychological, but it affects people physically. It's a matter of science, but scientists who discuss it can sound poetic. Dr. Katherine Shear, professor of psychiatry at Columbia University School of Social Work in New York, calls grief "the form that love takes when someone we love dies."

COVID-19 has both brought grief and disrupted the way people experience it. But researchers have been examining grief since well before the pandemic.

Simply defining it can be difficult. Shear, who also is director of the Columbia Center for Complicated Grief, said "there are pretty much as many different definitions of grief as there are people." Commonly, it's thought of as a feeling, like sadness. That's not wrong, she said, but it's more accurate to call it "the response to loss," a complex and multifaceted thing with yearning and longing at its core.

Its health implications are serious.