addiction: The National Institute of Drug Abuse defines this as a complex chronic disorder that is characterized by a difficult-to-control compulsion to use some drug, despite knowing that it will likely have harmful impacts. A first exposure to these drugs is usually voluntary. But repeated use of certain ones, NIDA explains, can create “changes to brain circuits involved in rewards, stress, and self-control.” Those changes can make it very hard to resist the urge to continue using drugs. The term has also been expanded to some behaviors that become dangerous and/or excessive, such as gambling, shopping and video game use.
adolescence: A transitional stage of physical and psychological development that begins at the onset of puberty, typically between the ages of 11 and 13, and ends with adulthood. People undergoing this transition are known as adolescents.
anxious: (n. anxiety) A feeling of dread over some potential or upcoming situation, usually one over which someone feels they have little control.
average: (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
brain scan: A technique to view structures inside the brain, typically with X-rays or a magnetic resonance imaging (or MRI) machine. With MRI technology — especially the type known as functional MRI (or fMRI) — the activity of different brain regions can be viewed during an event, such as viewing pictures, computing sums or listening to music.
cell: (in biology) The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells.
chemical signal: A message made up of molecules that get sent from one place to another. Bacteria and some animals use these signals to communicate.
chemistry: The field of science that deals with the…
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