In the letter, sent last week, doctors described the lockdown as a "mass casualty incident".

"We are alarmed at what appears to be the lack of consideration for the future health of our patients. The downstream health effects of deteriorating a level are being massively under-estimated and under-reported. This is an order of magnitude error," it states.

Written by Simone Gold, a California emergency medical specialist, and further signed by hundreds of doctors, the letter adds "The millions of casualties of a continued shutdown will be hiding in plain sight, but they will be called alcoholism, homelessness, suicide, heart attack, stroke, or kidney failure."

"In youths it will be called financial instability, unemployment, despair, drug addiction, unplanned pregnancies, poverty, and abuse," the letter further urges.

It notes that "Suicide hotline phone calls have increased 600%," while sales of alcohol have increased 300% to 600%.

"Because the harm is diffuse, there are those that hold it does not exist. We, the undersigned, know otherwise," the letter concludes.