Matthew Morrison struggled with his mental health amid 'Glee's success.

The 45-year-old actor played Will Schuester on the hit TV show between 2009 and 2015, but Matthew struggled to deal with the pressure and scrutiny that came his way.

During an appearance on the 'And That’s What You Really Missed' podcast, Matthew explained: "I was so stressed, I broke into the craziest psoriasis."

Matthew's physical wellbeing suffered amid the stress.

The actor said: "[I had] some super high highs, but also some really devastating lows. Our bodies are not designed to go through that kind of pressure."

Matthew believes that his psoriasis - which is a skin condition that causes flaky patches of skin - stemmed from the pressure and stress.

He explained: "I think it was just everything building up and, for me that was just the physical manifestation of what I was feeling inside. The psoriasis was everywhere on my body but my face was okay. But then it slowly started coming to to my ears and eyelids."

Matthew was very aware of fan comments and criticism at the time.

He shared: "You have all these news feeds coming out, like, bashing the way you’re playing your character or people trying to tear you down. All of this had a huge impact on my life."

Despite this, Matthew feels very proud of the show and his part in its success.

He said: "In a nutshell, I loved the experience and I appreciated it for what it was, but it was really challenging and it was hard to put our bodies through 16 hours a day and then all the other stuff we had to do on top of it.

"And not, like, woe is me, because it was an amazing opportunity, but we were all there, it was like a war."