Psychology of Substance Use: Definitions of Tolerance, Dependence, and Drug Types

Tolerance

Needing increasing amounts of a drug to achieve the desired effects.

Withdrawal

Experiencing negative side effects after stopping a drug.

Dependence

The physical or psychological need for a drug to maintain normal functioning.

Depressants

Slow the central nervous system.

Alcohol

Inhibits the excitatory neurotransmitter Glutamate (impairing memory) and increases the effectiveness of the inhibitory neurotransmitter GABA (creating relaxation).

Stimulants

Increase the activity of the nervous system.

Caffeine

Works by blocking the inhibitory neurotransmitter adenosine.

Nicotine

Stimulates the release of acetylcholine.

Cocaine

Prevents the reuptake of dopamine, prolonging its effects.

Amphetamines

Both inhibit the reuptake and stimulate the release of dopamine.

Opioids

Attach to the body's natural opiate receptors (which normally respond to endorphins) to cause pain relief and euphoria.

Fentanyl

A very powerful synthetic opioid used for severe pain.

Hallucinogens

Distort perceptions and evoke sensory images without sensory input.

LSD

Acts as an agonist of serotonin, particularly in the thalamus.

MDMA (Ecstasy)

A stimulant and hallucinogen known as an 'empathogen' that enhances empathy. It is a serotonin agonist and also increases dopamine. It is being researched for the treatment of PTSD.

Cannabis (Marijuana)

Works on the brain's natural endocannabinoid system. Medical uses include pain relief, appetite stimulation, and control of nausea and seizures.