How long does it take to write a book?

As someone who is currently attempting to write their first novel, I can't stop thinking about how long this process might take.  The blank page is scary!  I asked some inspirational authors how long it took them to write their first book.  The variations between answers may surprise you...

Cally Taylor- It took me just under 4 months to write the first draft then another 6 months or so to edit it.

Lorraine Wilson- about 3 months for the first chalet girl novella, a lot longer for a full length because I had a brain injury mid book!

Lucy Dillon- Er, about five months? It is the re-writing, re-writing and editing that take the extra time!

Rowan Coleman- About nine months, delivered just before my first child!

Sara Sheridan- 14 weeks.

Kat French- Undertaking Love took about eight months I think.

Miranda Dickinson- I was writing it for fun over seven years and then when it was signed by Avon I spent another eight months editing it.

Rebecca Raisin- 2 months to write and about six months to rewrite!

Louise Douglas- The first took about six months working in the evenings.  It was the quickest!

Mandy Baggot- About a year.

Let's just say that these responses have really encouraged me and I am realising that it really is a 'how long is a piece of string?' type question!