The former EastEnders star said the disease has badly affected her mental health.
Westbrook, 47, posted a series of videos to Instagram thanking a friend for taking her on a day out to FriendsFest, which celebrates the classic sitcom Friends with a replica set.
It was the first time she had left the house in a week and a half, she said.
She also shared a photo from the replica set and said the day out had been exactly what she needed.
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Actor Westbrook said: “So I had a great day at Friends Fest after coming out of COVID and literally a week and half of depression.
“It was severe, severe depression, I was literally getting out of bed just to eat and sometimes not even to wash, just to sleep, eat, use the bathroom.
“It was much needed that I got up and went out today and a huge thank you to my good mate Kelli Hollis and her family for coming to get me and making me leave the house, get up and get my s**t together.”
Westbrook added: “Depression is in all of us and none of us can escape it, it’s just how it manifests sometimes.
“For me, it’s particularly bad since I had COVID, but I feel like I have turned the corner so thank you guys. Thanks to my kids for their support, they have been on the end of the phone 24/7.”
Sharing with her fans how bad things had got, Westbrook said: "I really got in the doldrums, got down about stuff and even struggled to do a gratitude list some days and even reach out to my sponsor or pick up the phone to my kids. That's depression, that's what it does to you.
"I don't know what triggered it, I think being ill with COVID done it to me. I'm just grateful to be out the other side."
The actor added: "I know I'm not alone in a fight with depression, I know so many people suffer from it, and we're all just human beings at the end of the day."
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