Changes

Since the lust and attraction stages are both considered temporary, a third stage is needed to account for long-term relationships. Attachment is the bonding that promotes relationships lasting for many years and even decades. Attachment is generally based on commitments such as [[marriage]] and children, or on mutual friendship based on things like shared interests. It has been linked to higher levels of the chemicals [[oxytocin]] and [[vasopressin]] to a greater degree than short-term relationships have.

Since the lust and attraction stages are both considered temporary, a third stage is needed to account for long-term relationships. Attachment is the bonding that promotes relationships lasting for many years and even decades. Attachment is generally based on commitments such as [[marriage]] and children, or on mutual friendship based on things like shared interests. It has been linked to higher levels of the chemicals [[oxytocin]] and [[vasopressin]] to a greater degree than short-term relationships have.

The protein molecule known as the nerve growth factor (NGF) has high levels when people first fall in love, but these return to previous levels after one year.  “Raised plasma nerve growth factor levels associated with early-stage romantic love.” [http://www.biopsychiatry.com/lovengf.htm Abstract].

The protein molecule known as the nerve growth factor (NGF) has high levels when people first fall in love, but these return to previous levels after one year.  “Raised plasma nerve growth factor levels associated with early-stage [[romance|romantic]] love.” [http://www.biopsychiatry.com/lovengf.htm Abstract].

===Psychological basis===

===Psychological basis===