Drugs work by altering the chemistry of the brain.  Drugs of abuse, such as nicotine, cocaine and marijuana, work by affecting the brain’s signaling system.  This system is made up of billions of cells called neurons, which send and receive messages to and from other neurons.  Messages travel through neurons as electrical signals, which cause the release of a type of chemical at the neuron’s end called a neurotransmitter to pass the signal on to other neurons.

Some drugs are similar in size and shape to neurotransmitters.  This similarity allows them to attach to neurons and start a chemical chain reaction that leads to the release of large amounts of a neurotransmitter called dopamine.  Others can block neurons from reabsorbing dopamine for re-use, allowing too much of the chemical to pool in the signaling area between neurons.  Too much dopamine is what leads to the powerful high or “rush” that drugs can produce.

The first time someone abuses a drug, he or she may feel intense pleasure.  Of course, drugs have other effects, too; a first-time smoker may cough and feel nauseated, while a first-time cocaine abuser might even have a heart attack or stroke.

The unusual amount of neurotransmitters in the brain begins to change the brain in a number of ways.  For example, the brain may compensate by producing fewer neurotransmitters.  Neurons may become less sensitive to signals from other neurons.  Some neurons may even die from the drug’s toxicity.

Continued drug abuse also disrupts the brain circuits involved in reward, motivation and control, leading to the disease of addiction.  No one knows how quickly this happens, but after enough exposure, an addicted person craves the drug like people crave food, water or air, linking it to their very survival.  Eventually, natural “rewards” like friends and family lose out to compulsive drug-seeking and abuse.

That’s why it’s critical to prevent drug use before it ever starts.  NIH’s National Institute on Drug Abuse (NIDA) is testing many approaches designed to prevent drug abuse among different populations, especially young people.  But prevention must start at home, with parents.  One of NIDA’s goals is to help parents understand the causes of drug abuse so they can help prevent it.