Young Adult vs Adult Fiction.

(http://thehui.files.wordpress.com/2009/09/old-couple-743330.html)

Some where between these perhaps?

(http://3.bp.blogspot.com/_h0OGhdVfTVA/R47OmwtH0FI/AAAAAAAAASE/L-bYfAFCEkg/s400/a_teens2_2.jpg)

Just busy writing away and thinking about the divide between young adult and adult fiction.

My protagonist is young ( early twenties) and the story is a coming of age story. Although there are older characters, the story centres on the life and times of the lead and friends growing up and finding themselves in the world. On this basis alone, I think it leads towards young adult fiction.

Now, there is no intention to litter the story with sex, drugs or violence but I don´t feel as if it is a story I would share with a 16 year old, even though most teenagers would relate to it.

Is there a definite divide between the two genres or is there some kind of middle ground? Would it be too ambitious to market an idea like this to a purely adult audience who might find certain parts rather juvenile?