Addiction to drugs and alcohol is a brain disease. Once addiction develops, the brain changes, interfering with a person's ability to make voluntary decisions, leading to compulsive drug craving, seeking and use. Words, thoughts and behaviour become dictated by the drug. Drugs temporarily provide a false sense of happiness, but after every high there is a great low that gets lower every time you take a drug, even the high. This is how people get addicted. They take it the second and then the third and so on to stay on that high and not get the low that follows.
By abusing drugs, the addicted teen has changed the users brain works. Drug abuse and addiction lead to long-term changes in the brain. These changes cause addicted drug users to lose the ability to control their drug use.