Scarlett Johansson says Black Widow ''grapples'' with the ''trauma'' she has experienced in the forthcoming Marvel films.

The 29-year-old actress reprises her role as the popular Marvel character - also known as Natasha Romanoff - in the 'Avengers: Age of Ultron', which will be released in 2015, and will tell the ''back story'' of the highly trained spy.

Talking at the press conference for forthcoming 'Captain America: The Winter Soldier', at London's Dorchester Hotel on Thursday (20.03.14), she said: ''You'll get more of Widow's back story in 'Avengers 2'. She has a rich, rich past. She definitely comes from a really dark past, she's had to de-sensitise or de-humanise in way to be able to do and see some of the things she's seen and participated in willingly. And there was probably some kind of people who have that drug description, like mercenary.

''I think she' s sort of now grappling with the fact that she maybe experiencing some trauma from that, or at least that she has feelings about things, maybe she doesn't sleep so well at night. It's hitting her now that she's been acting as a gun for hire, and in doing that she's never really made any active choices. It's like the rug has been pulled from under her feet.''

Marvel Studios President Kevin Feige previously confirmed he's been in talks about a film based on Johansson's Black Widow character, and the screen beauty insists she'd like to follow the ''progression'' of her alter-ego.

She added: ''More interestingly, what would probably be to follow the progression of that story. And you know, bring her back home, and see where that leads to. Of course that's all in my imaginary next installment. None of that has been .... We've thrown the ball around a little bit but nothing is in the works for that right now.''