The 28-year-old actor told E! News: "To be completely candid with you, I really struggled with my mental health like many people did throughout the pandemic."
The 'Dopesick' star said his role as Billy Cutler in the miniseries, created by Danny Strong and based on Beth Macy's 2018 book 'Dopesick: Dealers, Doctors and the Drug Company that Addicted America', also proved challenging mentally, reports femalefirst.co.uk.
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Poulter noted the cast and crew were "very empathic" towards him, and added: "I'm very grateful to them for that.
After filming finished on the show, Will took time out to visit his family as he put a renewed focus on his physical and mental health.
He said: "I am a big proponent of physical exercise and the natural endorphins that come from doing that as a means of improving your mental health."
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Poulter also makes sure to keep a "regulated distance from social media".
He said: "I try and maintain a kind of healthy and regulated distance from social media, because often on social media you're exposing yourself to the opinions of people that you don't know."