For a function of two variables z=f(x,y), the gradient is the two-dimensional vector <f_x(x,y),f_y(x,y)>. This definition generalizes in a natural way to functions of more than three variables. For the function z=f(x,y)=4x^2+y^2.
By this definition, about 10% of people who smoke marijuana become addicted to it. (More on Time.com: PHOTOS â Cannabis Conventions). However, nonspecialists (including many doctors) still tend to use an older perspective, now seen as outdated by experts.
Marijuana Fact: Marijuana can be addictive. About 1 in 6 people who start using as teens and 25 to 50 percent of those who use it every day become addicted. Long-term studies of drug use patterns show that most high school students who use other illegal drugs have tried marijuana first. However, many young people who use marijuana do not go on to use other drugs. To explain why some do, here are a few theories: 1  Exposure to marijuana may affect the brain, particularly during development, which continues into the early 20s. 2  Effects may include changes to the brain that make other drugs more appealing.