Linda Blair suffered a "midlife crisis" in her 20s

She told People magazine: "In my 20s, I said, 'I really am struggling.' It was like, for some, a midlife crisis. But, for me, it was my life's calling, saying, 'What about me? The animals need help.'

"So that's where I really started buckling down ... and I was giving my time and money."

Before being cast in 'The Exorcist', Linda had only taken on small acting and modelling jobs in order to help fund her goal of becoming a vet.

She explained: "It wasn't Hollywood. That wasn't what we signed up for. We weren't looking for that, we were looking for funding for me to pursue my dream, which was to go to Cornell [University]."

And she was thankful she was able to retain a normal life, with her love of animals at the heart of it, throughout filming.

She said: "They made sure on the weekends I went out. I got to ride my horses [and] I had raised a rooster in an incubator on the set for my science project."

However, when the movie became a huge hit, it "changed the direction" of Linda's ambitions.

She reflected: "So I worked and I worked. I'm proud, now, of all these movies ... and I know they changed a lot of lives, so for that, I am very grateful."

But Linda still wanted to help animals and in 2003, she launched the Linda Blair WorldHeart Foundation, which is dedicated to rescuing and rehabilitating abused, neglected and abandoned animals, though she still thinks there is more work to be done.

She said: "I think a lot of people in animal welfare need to get more involved so that we can make the changes that are necessary.

"But that requires funding. We get nothing from the state, nothing from the government. There is no financial aid for the rescue community. Shelters can keep applying for state funding, but not the rescue groups.

"That's why I've been saying, help in your area, volunteer, foster and adopt. Ask what can you do.

"You can do a bake sale and bring that money, or you could provide food and blankets as you're cleaning out your closet.

"And when it all comes down to voting [in] any of these elections, make sure you know who you're really voting for, because that is who dictates what you get in your life and the love that we can have on this planet."