Grant Gustin opened up about his life-long battle with his mental health issues and admits that his anxiety is the reason he is thin because it gets the better of his appetite.

"The Flash" star opened up about his battle with anxiety and depression during Tuesday's episode of "Inside of You with Michael Rosenbaum." He admitted that he developed problems early on in childhood, "since probably four or five [years old]."

"I've had really weird anxious type dreams that's like a really young kid," Gustin shared, and revealed that he and his wife Andrea Thoma even went into couples therapy prior to getting married just to prepare themselves for whatever "comes to the surface" when they are married.

"I knew I had always dealt with anxiety," he continued, adding that "anxiety is ever-present" in his life.

Gustin said his anxiety also manifests at work or on set because he puts a lot of focus on getting things right. He admitted that he can be a d**k when he gets stressed out because he thinks that others do not feel the same way he does. But he has since learned during his journey on "The Flash" that everyone else has their own worries or problems to deal with and that they deal with the stress at work in their own way.

"I've always been really hard on myself and I still am, but I put way too much pressure on myself early on and got in my way a lot and I think it shows, in my opinion at least, in the work, like how wound up I was and how focused I was on getting it right. It gets in your way for sure," the 30-year-old former "Glee" star told Rosenbaum, and added that he has since taken a little of that pressure off himself.

Interestingly, Gustin said that his anxiety gets so bad the morning before Comic-Con. He gets so nervous that he does not have the appetite to eat for the day. He said "it's really bad" and claimed that his anxiety is one of the reasons he is "so thin."

Grant Gustin
Grant Gustin plays Barry Allen on The CW series "The Flash." Vivien Killilea / Getty