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Addiction: A chronic, relapsing disease characterized by compulsive drug seeking and use and by long-lasting changes in the brain.

Basal Ganglia: Structures located deep in the brain that play an important role in the initiation of movements. These clusters of neurons include the caudate nucleus, putamen, globus pallidus, and substantia nigra. It also contains the nucleus accumbens, which is the main center of reward in the brain.

Cerebellum: A large structure located in the back of the brain that helps control the coordination of movement by making connections to other parts of the CNS (pons, medulla, spinal cord, and thalamus). It also may be involved in aspects of motor learning.

Cerebral Cortex: The outermost layer of the cerebral hemispheres of the brain. It is largely responsible for conscious experience, including perception, emotion, thought, and planning.

Cannabinoids and Cannabinoid Receptors: A family of chemicals that bind to specific (cannabinoid) receptors to influence mental and physical functions. Cannabinoids that are produced naturally by the body are referred to as endocannabinoids. They play important roles in development, memory, pain, appetite, among others. The marijuana plant (Cannabis sativa) contains delta-9-tetrahydrocannabinol (THC) that can disrupt these processes, if administered repeatedly and/or in high enough concentrations.

Carcinogen: Any substance that causes cancer.

Cognitive-Behavioral Therapy (CBT): A form of psychotherapy that teaches people strategies to identify and correct problematic behaviors in order to enhance self-control, stop drug use, and address a range of other problems that often co-occur with them.

Contingency Management (CM): A therapeutic management approach based on frequent monitoring of the target behavior and the provision (or removal) of tangible, positive rewards when the target behavior occurs (or does not). CM techniques have shown to be effective for keeping people in treatment and promoting abstinence.

Dopamine: A brain chemical, classified as a neurotransmitter, found in regions of the brain that regulate movement, emotion, motivation, and pleasure.

Hippocampus: A seahorse-shaped structure located within the brain that is considered an important part of the limbic system. One of the most studied areas of the brain, the hippocampus plays key roles in learning, memory, and emotion.

Hydrocarbon: Any chemical compound containing only hydrogen and carbon.

Motivational Enhancement Therapy (MET): A systematic form of intervention designed to produce rapid, internally motivated change. MET does not attempt to treat the person, but rather mobilize their own internal resources for change and engagement in treatment.

Psychosis: A mental disorder (e.g., schizophrenia) characterized by delusional or disordered thinking detached from reality; symptoms often include hallucinations.

Schizophrenia: A psychotic disorder characterized by symptoms that fall into two categories: (1) positive symptoms, such as distortions in thoughts (delusions), perception (hallucinations), and language and thinking and (2) negative symptoms, such as flattened emotional responses and decreased goal-directed behavior.

Schizophreniform Disorders: Similar to schizophrenia, but of shorter duration and possibly lesser severity.

THC: Delta-9-tetrahydrocannabinol; the main active ingredient in marijuana, which acts on the brain to produce its effects.

Ventral Striatum: An area of the brain that is part of the basal ganglia and becomes activated and flooded with dopamine in the presence of salient stimuli. The release of this chemical also occurs during physically rewarding activities such as eating, sex, and taking drugs, and is a key factor behind our desire to repeat these activities.

Withdrawal: Adverse symptoms that occur after chronic use of a drug is reduced or stopped.

This page was last updated July 2012

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​Research Reports

This series of reports simplifies the science of research findings for the educated lay public, legislators, educational groups, and practitioners. The series reports on research findings of national interest.