The actress, who plays Liz McDonald in the long-running soap, ended up almost £150,000 in debt after two pubs she ran with her partner, John, went bust in 2008.
A year later she suffered a panic attack, was diagnosed with clinical depression and admitted to a psychiatric hospital.
Her son Josh told Piers Morgan his mother was "suicidally low" and "wanted to die most of the time".
Appearing on the former newspaper editor's Life Stories show, she said she came very close to taking her own life.
She said: "I tried maybe half a dozen times, but it wasn't a cry for help at all. I'd known for quite a while that I wasn't myself, but I didn't really know what to do about it.
"I was going to work and I was still filming and I didn't really talk to anyone about it and on that day they took me into The Priory in the early hours of the next morning and John said, and my doctor said, I looked like a 100-year-old woman. They tried different medications but none of them seemed to work."
Doctors gave her electroconvulsive therapy (ECT) which had the side-effect of destroying her short-term memory, making it difficult to learn her lines.
She said: "I actually, now, don't know how I learnt my lines.
"It was really a double life at that point. People stand on the gate waiting to meet people who are in Coronation Street and I couldn't sign my autograph because I couldn't remember how to spell my name. I truly couldn't write my name for the first six months."
The actress said she would stay on medication for "at least another couple of years" to keep her from "going into that black hole".
Callard, who has been married four times, also revealed she had an affair with Emmerdale co-star Ian Sharrock.
:: See the full interview on Piers Morgan's Life Stories: Beverley Callard on ITV at 9pm tonight.