Natalie, I am glad that you have not experienced any depression.  You need to keep in mind that one experience, such as yours does not invalidate the statistical evidence of many.  There are always exceptions.  

I was born at 34 weeks and had a good birth weight (5lbs 6 ounces).  I was in the NICU for 2 weeks.  This was back in the early 80's when they did not dim the lights ir allow the mother to hold or touch the baby in the isolette.  They are now trying to make the NICU surroundings as unintrusive and gentle as possible.  You were likely born when they started making changes to the NICU and allowed "Kangaroo Care" with your mother.  The bright lights, loud alarms sounding, the constant probing and lack of physical contact in the NICU was much worse 30 years ago.  It has been shown to contribute to psychological trauma in premature and ill neonates.