Psychoactive Drugs, the Brain, and Substance Use Disorders

Vocabulary flashcards detailing the mechanisms of psychoactive drugs, synaptic transmission, neurotransmitter systems, and the relationship between substance abuse and mental illness.

Psychoactive Drugs

Chemical substances that affect the way the brain transmits impulses across synapses and can alter the functioning of the brain and personality.

Excitatory Drugs

Psychoactive substances that stimulate nervous system transmission and brain activity, specifically including cocaine, amphetamines, and nicotine.

Inhibitory Drugs

Psychoactive substances that slow or suppress synaptic transmission in the brain, specifically including benzodiazepines, alcohol, and THC.

Nicotine

A stimulant drug that binds rapidly to acetylcholine receptors in synapses, binds to dopamine receptors causing long-lasting changes to cell connections, is not broken down by enzymes, and reduces the body's ability to produce its own dopamine.

Dopamine Transport Sites

Proteins in the presynaptic bulb that reabsorb dopamine back into the bulb; they are blocked by cocaine and amphetamines, causing dopamine to accumulate in the synapse.

Amphetamines

Stimulant drugs that work by blocking dopamine transport sites to cause synaptic dopamine buildup, producing increased energy, high addiction potential, and possible mental health issues like paranoia, depression, and delusions with prolonged use.

Ethanol

A fat-soluble sedative substance that enters and alters the properties of cell membranes, modifying multiple neurotransmitter systems including glutamate, GABA, dopamine, and endorphins.

Glutamate System (Alcohol Interaction)

The neurotransmitter system inhibited by alcohol (similar to ether and chloroform), resulting in muscular relaxation, discoordination, slurred speech, staggering, memory disruption, and blackouts.

GABA (Gamma-Aminobutyric Acid)

A major inhibitory neurotransmitter whose receptor function is enhanced by alcohol and benzodiazepines to slow nerve impulses and elicit feelings of calm, anxiety reduction, and sleep.

Endorphin System (Alcohol Interaction)

The neurotransmitter pathway in which alcohol raises neuropeptide levels to relieve pain and induce an endorphin high, producing effects similar to morphine and heroin.

Tetrahydrocannabinol (THC)

The active cannabinoid ingredient in cannabis that acts as a sedative by binding to cannabinoid receptors and mimicking the action of the endogenous neurotransmitter anandamide.

Anandamide

A naturally occurring cannabinoid neurotransmitter that activates cannabinoid receptors in the brain and whose actions are mimicked by THC.

Hippocampus (in Cannabinoid Action)

A brain area containing high concentrations of cannabinoid receptors that regulates short-term memory; THC binding here interferes with the recollection of recent events.

Cerebellum (in Cannabinoid Action)

A brain region with dense cannabinoid receptors responsible for motor coordination, which becomes impaired when THC binds to its receptors.

Basal Ganglia (in Cannabinoid Action)

A brain region rich in cannabinoid receptors that controls unconscious muscle movements, contributing to impaired motor coordination under the influence of marijuana.

Benzodiazepines

Sedative medications that enhance the inhibitory activity of GABA on motor neurons; they target two distinct receptor types: one mediating anti-anxiety effects and the other mediating sedative effects.

Substance Use Disorder

A condition involving the excessive use of alcohol, tobacco, or other drugs, also commonly referred to as substance dependence or addiction.

Substance Abuse vs. Substance Dependence

Two stages defined on a scale of time and degree of substance use, where abuse serves as an early stage that increases the risk of developing a full dependence disorder.

Prevalent Abused Substances in Australia

The legal substances nicotine (tobacco or vapes) and alcohol are the most commonly abused, while the most commonly used illegal drugs are cannabis, ecstasy, cocaine, and methamphetamines.

Smoking Disease Burden (Australia)

The single most preventable cause of sickness and death in Australia, where approximately $13\%$ of people aged $14$ and over smoke daily, accounting for nearly $8\%$ of the total disease burden.

Risky Alcohol Consumption (Australia)

A public health concern where just under $1\text{ in }6$ Australians drink alcohol at risky levels, predisposing them to accidents, violence, liver disease, and mental disorders.

Dual Diagnosis

The clinical co-occurrence of a mental illness and a substance abuse disorder in the same person.

Drug-Induced Psychosis

A temporary psychotic state brought on by drug use that usually resolves within days, but can trigger the initial episode of a lifelong psychotic illness such as schizophrenia in predisposed individuals.

Self-Medication Hypothesis

The tendency of individuals to abuse alcohol or drugs in order to temporarily relieve the distressing symptoms of an undiagnosed or underlying mental illness.

JAMA Comorbidity Statistics

Findings showing roughly $50\%$ of individuals with severe mental disorders have substance abuse, $37\%$ of alcohol abusers and $53\%$ of drug abusers have a serious mental illness, and $29\%$ of all diagnosed mentally ill individuals abuse substances.

Global Alcohol Mortality and Consumption

Harmful alcohol use causes $3.3\text{ million}$ deaths globally each year; while the average person aged $15+$ drinks $6.2\text{ litres}$ of pure alcohol annually, the $38.3\%$ who actually consume alcohol average $17\text{ litres}$ per year.

Global Injecting Drug Comorbidities

Out of nearly $11\text{ million}$ people globally who inject drugs, $1.3\text{ million}$ live with HIV, $5.5\text{ million}$ with hepatitis C, and $1\text{ million}$ with both HIV and hepatitis C.

Genetic Variants (Switches)

Biological risk factors for substance use that operate like switches (either turned on or off), whose gene expression is regulated by epigenetic modifications based on life experience.

Environmental Factors (Dials)

External adversity and resilience influences that act like dials turned up or down throughout life to modify a person's liability threshold for substance use disorders.

Intermediate Phenotype

Neurobiological traits comprising brain structure, function, and behavioral modifications (such as self-regulation, mood stability, novelty seeking, and impulsivity) that mediate between genes, environment, and drug use disorders.

Telescoping

The gender-based clinical phenomenon where more men than women initiate drug use, but women accelerate more rapidly from initiation to drug use disorders.