Not to be confused with other types of electrography or with echocardiography. Electrocardiography (ECG or EKG) is the process of recording the electrical activity of the heart over a period of time using electrodes placed on the skin.
Addiction is defined as a chronic, relapsing brain disease that is characterized by compulsive drug seeking and use, despite harmful consequences. It is considered a brain disease because drugs change the brain; they change its structure and how it works.
Gateway drugs are substances that when consumed give way to harder, more dangerous drugs. These milder substances, such as nicotine or alcohol, are believed to open the door to drugs such as meth, heroin and cocaine, which can lead to addiction. Gateway drugs boost dopamine levels, which increases pleasure.