My kitchen bench is covered with vitamins and protein powders. I go through phases when I'm sure I'm taking too many - but I don't get sick often.

Happy songs are very difficult to write. How many truly great upbeat songs are there?

I worry unnecessarily.

I exercise three to four times a week, doing the Tracy Anderson Method, which involves toning and strengthening our small muscle groups.

I can understand why some people might look at me and say, 'What's she got to be depressed about?' I get that a lot in Britain, where mental health issues seem to be a big taboo.