Amber Riley's mental health struggles led to insomnia.

The 37-year-old actress thinks it is "important" for people to realise that mental health and physical health go hand-in-hand and has recalled a time that she would find herself "comfort eating" in the middle of the night as she admitted that even her heart rate has been affected by her stress levels.

She told Variety: "It’s important that people understand that your mental health can affect your physical. Mental health can also affect your heart too.

"My stress really started to manifest itself habitually with insomnia – not sleeping, overthinking, not getting enough rest. When I was younger, it definitely manifested itself with eating, which I didn’t know. I didn’t understand why I was getting up at two in the morning, sneaking downstairs to get chips. It was just comfort-eating and not really being conscious of it.

"I get sluggish, a little bit slow and even heart palpitations or heart beating fast or feeling like that fight or flight kind of kicks in sometimes. That’s mainly how it manifests itself in my body. It’s very, very physical. Sometimes people don’t know depression or anxiety can be physical. They think it’s all just in your head."

The former 'Dancing with the Stars' winner shot to fame when she was cast as Mercedes Jones on 'Glee' in 2009 and went on to recall that she suffered her first panic attack during her first day on set of the musical drama series.

She said: "I had my very first panic attack on the very first day of filming. I just stepped up and froze. It was a highly stressful situation because messing up your line means everybody has to start over again, so everybody in the room is depending on you. I only had one line so the stress and the pressure of just getting it right … The rest of the actors were all collectively kind of freaking out because we just weren’t expecting all eyes to be on us."