Ethan Hawke has insisted Robin Williams' mental health struggles were "obvious".

The Training Day actor starred with the late comic - who took his own life in 2014 at the age of 63 - in the 1989 classic movie Dead Poets Society and he insisted the death of Robin doesn't change how he looks at Peter Weir's movie now because he was always aware of his co-star's "complex" feelings.

Speaking on CBS Sunday Morning, Ethan said:

"It does not fundamentally change the way I watch the movie because, even at 18, I was aware of the complexity of his emotional life.

"I've had a lot of depression in my family, and it was obvious to me that all that power and that charisma came at a certain cost. [He was] a deeply, deeply sensitive person, who was highly attuned to the energy of a room."

The 55-year-old star recalled one particular moment where he could see Robin's struggles during a moment on set.

He said: "I remember, once, he was making up lines, and everybody's laughing and everybody's praising him, and I went to get a glass of water, get a bagel or something, and I saw him hiding in a little corner, just hiding in the dark, by himself.

"And I [go], 'Oh, OK.' It makes a lot more sense to me now, actually. It was a lot; it was taxing. There's a lot of stories about clowns and the happiness that they give and at what cost.

"So, I say all that to say, the end of his life does not define his life to me.

"When I watch the movie, I think of the spirit of the man that I knew on those days and how powerful it was and how much he weathered that storm of his own psyche for us and for other people. I admire him tremendously. There aren't two of him."

Ethan previously credited Robin for helping to kickstart his Hollywood career following their experience on Dead Poets Society.

Speaking on The Graham Norton Show in 2018, he said: "After the movie came out I got a call from Robin's agent asking to represent me as Robin had told him I was going to be someone one day. He was a lovely, gentle man."

And Ethan was almost ready to give up acting before making his breakthrough in the movie and was ready to "join the marines" instead.

He said: "That film was 'make or break' for me. I told my sister that if I didn't get the role then I would join the marines or something."