concussion Bruise on the surface of the brain; the mildest and most common type of brain
injury.
depressant drug Psychoactive drug that slows down the nervous system.
drug Any chemical substance that affects the body or brain.
drug abuse Use of a drug without the advice of a doctor or for reasons other than those
for which the drug was intended.
drug addiction Condition in which a drug takes over people’s lives and they cannot stop
using the drug even if they want to.
drug overdose Taking so much of a drug that it causes serious illness or death.
encephalitis Infection of the brain that is usually caused by viruses.
epilepsy Disease in which seizures occur.
hallucinogenic drug Psychoactive drug that can cause strange sensations, perceptions,
and thoughts.
meningitis Viral or bacterial infection of the membranes that cover the brain and spinal
cord.
migraine Severe type of headache that occurs when blood vessels in the head dilate.
paralysis Inability to feel or move parts of the body.
physical dependence Condition in which drug abusers need a drug to feel well physically.
psychoactive drug Drug that affects the brain and influences how a person feels, thinks,
or acts.
psychological dependence Condition in which drug abusers need a drug to feel well
emotionally.
Reye’s Syndrome Rare, potentially fatal condition associated with aspirin use in young
people with viral infections.