Marion Cotillard had panic attacks while shooting 'Macbeth'.

The 39-year-old actress stars as Lady Macbeth opposite Michael Fassbender in the titular role in the big screen adaptation of the Shakespeare play.

Although she has been making movies for the past three decades, Marion started suffering from the cripplingly bouts of fear on set because she was being pushed to her absolute physical and mental limits.

In an interview with the new issue of Porter magazine, she revealed: ''When I start a movie I usually freak out ... This time it was pretty physical and intense. Panic attacks ... I never had panic attacks before. What was funny is I didn't know what a panic attack was, but I had studied it for the role I did before (in 'Two Days, One Night').''

Although Marion had never had panic attacks before her research for 'Two Days, One Night' helped her cope with them.

The French beauty was willing to accept the medical condition because the role of Lady Macbeth meant so much to her.

Marion - who is in a long-term relationship with Guillaume Canet, with whom she has four -year-old son Marcel - explained: ''When (I had one) I knew exactly what it was and I was like, 'Are you kidding me? Am I having a panic attack?!' But I just had to accept I would freak out the whole shoot long. That was not very comfortable, but you don't expect to be comfortable playing Lady Macbeth ... You make the choice of living a nightmare and you deal with it.''