Every chemical or inorganic substance that a person needs to take larger and larger doses to get the same initial effect is because he has developed tolerance to that substance. An example of this can be seen in the question above, where Kristen only needed to take 3-5 cigarettes a day to feel safe and in control of her life. However, this amount of cigarettes is no longer enough to promote these feelings in Kristen, because she has developed cigarette tolerance and needs to smoke more to feel peaceful and in control of her life.
