Addiction: a brain disease that is characterized by compulsive substance or behavior seeking and use despite harmful consequences

Amphetamine: central nervous system stimulant drugs prescribed for the treatment of narcolepsy, hyperactivity (e.g. ADHD) and asthma

Amygdala: a roughly almond-shaped mass of grey matter inside each cerebral hemisphere, involved with the experiencing of emotions

Cannabinoids: chemicals that bind to cannabinoid receptors in the brain, which are found naturally in the brain and are also found in marijuana and are involved in a variety of mental and physical processes

Central nervous system: the brain and spinal cord, which control all the body’s functions by sending and receiving messages through nerves

Dependence: a physical state in which the person only functions normally when using the substance

Dopamine: a brain chemical, or neurotransmitter, found in the brain that regulates movement, emotion, motivation and pleasure

Dysphoria: a profound state of unease or dissatisfaction, which may accompany depression, anxiety or agitation

Equilibrium: state of rest or balance due to the equal action of opposing forces

Euphoria: a state of intense happiness and self-confidence

“Fight-or-flight” response: our instinctual reactions to stress, which evolved as a survival mechanism, enabling people and other mammals to react quickly to life-threatening situations

Hallucinations: perceptions of something (such as an image or a sound) that does not exist in the real world

Inhibition: an inner restraint or holding back to free activity, expression, or functioning

Misuse: use of a substance for a purpose not consistent with legal or medical guidelines

Narcotic: a drug, such as morphine or heroin, that is derived from opium or an opium-like compound, relieves pain, often induces sleep, can alter consciousness, and is potentially addictive

Myelin: fatty material that surrounds and insulates most neurons to maximize the transmission of information

Neurons: nerve cells found in the brain and throughout the body that specialize in the transmission and processing of information

Neurotransmitter: a chemical produced by neurons to carry messages to adjacent neurons, which are found in the brain and throughout the body to send and process information

Norepinephrine: a stress hormone and a neurotransmitter that affects parts of the brain where attention and responses are controlled; part of the fight-or-flight response

Psychoactive: having a specific effect on the brain

Psychosis: a state of mind where a person’s thoughts and perceptions are disturbed making it hard for them to understand what is real and what is not

Receptor: a large molecule located on the surface of a cell that recognizes specific chemicals, such as neurotransmitters and hormones, and transmits the chemical message into the cell

Relapse: the return of a disease weeks or months after its apparent end or improvement

Reward system: a brain circuit that, when activated by dopamine-containing neurons, fortifies behaviors

Serotonin: a neurotransmitter that regulates many functions, including mood, appetite, and sensory perception

Synapse: a small gap separating neurons, which requires an electrical impulse to carry information from one neuron to another neuron

Synthetic: compounds formed through a chemical process by humans, as opposed to those of natural origin

Tolerance: a condition in which higher doses of a substance are required to produce the same effect achieved during initial use

Withdrawal: symptoms that occur after a person abruptly reduces or stops long-term use of a drug, which can vary in length and intensity depending the type of drug; often flu-like symptoms, such as muscle and bone pain, insomnia, diarrhea, vomiting and cold flashes, but also restlessness, depression or dysphoria