I think that there is a strong correlation between attachment style as a child and attachment style as an adolescent and adult. Things you learn as a child and experiences that you have are more often the first experiences you are having at that time and this causes a lasting memory to be formed of what that situation is like, such as being left at school or having your parents leave on a trip or just being home with a babysitter. These experiences are new and frightening but so long as the child learns early on that his or her parents are coming back the attachment style will be more secure.
I do think however that as one gets older it gets harder adn harder to change the attachment style. relationships with family and friends and significant others may further shape attachment styles in adolescence, but those same situations may not affect an adult quite as much.
