I doubt it. Your body is probably just accustomed to nortriptyline in order to sleep. This is an antidepressant and people miss taking medications all of the time. This isn't a narcotic, I don't believe. It's other name is Pamelor and I had a friend taking this for depression. She has taken it for over 25 years.
If you ever do want to stop taking this, you need to wean yourself off of it.
Sherrine