The Cambridge professor said suffering from "great pain" would also lead him to think about ending his life.
Hawking added he's not planning on giving up any time soon, saying: "I am damned if I’m going to die before I have unravelled more of the universe."
Speaking of the hardships of living with motor neurone disease, Hawking said it can be lonely not being able to communicate in the same way as many other people.
"At times I get very lonely because people are afraid to talk to me or don’t wait for me to write a response," he said.
"I’m shy and tired at times. I find it difficult to talk to people I don’t know."
It is not the first time Hawking has voiced support for assisted suicide – in 2014, he revealed in a BBC interview how he had attempted to die after a mid-1980s tracheostomy operation. “I briefly tried to commit suicide by not breathing,” he said. “However, the reflex to breathe was too strong.”
Hawking, who is the director of research at the Centre for Theoretical Cosmology at the University of Cambridge, has said those who help their loved ones who want to die should be immune from prosecution.
But he has also said he believes safeguards should ensure a person genuinely wishes to die, pointing to a famous incident in his own life. In 1985, when suffering complications from pneumonia, his then-wife, Jane, refused to turn off his life support machine. Hawking recovered and went on to complete his critically and popularly acclaimed book A Brief History of Time.
