The acting icon stars as Grace, alongside Lily Tomlin as Frankie, in the popular Netflix comedy, in which the characters' lives are turned upside down when their husbands reveal they are gay - and have fallen in love with one another.
Fonda, who has accused each of her three ex-husbands of infidelity during their marriages, admits the premise for Grace's emotional unravelling hit a little close to home, and it ended up sending her running to her therapist.
"It took me a season to come to care for my character," she confessed to The Hollywood Reporter. "I had to go back into therapy and start Prozac (antidepressant)...".
"I had a nervous breakdown during the first season and I discovered it's because the very first episode, our husbands tell us that they are going to leave us after 40 years and marry each other and that triggered abandonment...".
Fonda, who has since grown to really like her TV alter ego, continued, "It was a big trigger, and I didn't realise that a character in a comedy could actually trigger something very profound. And so I love her and I learned to invite her into the room."