One critical point made regarding our individual set point is to understand it may simply be a genetic tendency and not a completely determined criterion for happiness, and it can still be influenced. In a study on moderate to excessive drug intake on rats, Ahmed and Koob (1998) sought to demonstrate that the use of mind-altering drugs such as cocaine could change an individual's hedonic set point. Their findings suggest that drug usage and addiction lead to neurochemical adaptations whereby a person needs more of that substance to feel the same levels of pleasure. Thus, drug abuse can have lasting impacts on one's hedonic set point, both in terms of overall happiness and with regard to pleasure felt from drug usage.