Carey Mulligan finds it ''terrifying'' that she's in her 30s.

The 'Great Gatsby' star - who turned 33 in May - admits she found it difficult when her 20s ended.

She told People and Entertainment Weekly at the Toronto International Film Festival: ''The thing I more identified with was the idea that my 20s have gone. I'm not 20 anymore and you hear a song that you sort of listened to when you broke up with boyfriend when you were 18. And you hear that now and think, 'What, I'm a grown up?!' It's terrifying!''

Meanwhile, Carey previously confessed she is terrified she's going to develop dementia.

She said: ''Recently, I was asked if I fear dementia. My answer was yes - but this isn't a bad thing, because fear propels me into action. Action to make change happen. To change life for the better and, intimately, find a cure. The misconception that the symptoms people with dementia display, such as memory loss and confusion, are just an unfortunate consequence of old age is extremely damaging. It creates stigma, it isolates and marginalises people with the condition and their families and it slows us down in our search for a cure.

''If this is just something that happens to the unlucky, if this is just granny losing her marbles then why bother to find a cure? It's crucial we understand it is a disease we need to fight through care, research and drug development funding in the same way that we fight diabetes or cancer.''