Drugs, Brain and Behaviour (1): Intro

What is a drug?

• Any substance that affects physical or mental functioning (OED definition).

• A chemical entity that alters biological functioning (WHO definition).

How are drugs classified?

• Source (Natural, semi-synthetic, and synthetic)

• Chemical structure (Grouping drugs based on molecular structure (e.g., phenethylamines, benzenoids).

• Mechanism of action (Grouping drugs based on how they act biologically (e.g., opioids acting on opioid receptors).

• Therapeutic use (Grouping by medical use (e.g., analgesics, anxiolytics, antiemetics).

• Behavioural effect (Grouping based on effects on mood, cognition, behaviour, and consciousness (e.g., stimulants, sedatives, hallucinogens).

• Social/legal status (Grouping by legal status (legal, controlled, illegal).

• Street names.

Naturally occurring drugs

Drugs derived directly from plants or natural sources (e.g., opium → morphine; coca → cocaine; ephedra → ephedrine).

Semi-synthetic drugs

Drugs chemically modified from natural substances (e.g., heroin from morphine; LSD from ergot fungus).

Synthetic Drugs

Fully laboratory-made drugs, often called “designer drugs” (e.g., methadone, amphetamine, fentanyl, MDMA).

Why do different classifications matter?

Different systems create different labels and interpretations of drugs.

Misuse of Drugs Act 1971

UK law controlling possession, supply, manufacture, and import/export of controlled drugs, based on UN conventions. → To prevent misuse of drugs.

Human Medicines Regulations 2012

UK regulations controlling medicinal products.

Psychoactive Substances Act 2016

UK law controlling “legal highs” and new psychoactive substances affecting mental functioning.

Which substances are regulated separately from UK drug laws?

Alcohol and tobacco.

Drug harm rating system

A system evaluating drugs based on:

• Physical harm

• Dependence

• Social harm

What did David Nutt (2015) find about drug harm?

Found major disagreement between legal status and actual harm of drugs. → Drug laws do not always reflect scientific evidence.

What are the main reasons people use drugs?

• Experimentation

• Curiosity

• Novelty seeking

• Pleasure

• Reward

• Self-medication (Using drugs to cope with stress, anxiety, or pain.

• Social factors. (Peer pressure and social acceptance.

Why does drug use does not always equal addiction?

Many people use substances without becoming addicted.

What is NOT addiction?

• Experimental use

• Recreational use

• Stuational use

What is the DSM-5 approach to substance-use disorders

Uses a severity scale (mild to severe), includes behavioural addictions, removes legal problems as criteria, and adds craving.

Addiction

• A behavioural pattern where drug use is prioritised over other activities, involving compulsive use and loss of control. (WHO definition of addiction - 1981)

• A chronic relapsing disorder (Jaffe, 1990)

Key features of Addiction

• Compulsivity

• Loss of control

• Priority shift (When drug use becomes central and more important than other life activities).

• Persistence (Continued drug use despite harmful consequences).

• Relapse (Returning to drug use after a period of abstinence).

• Brain changes (Neural adaptations underlying compulsive drug use).

What is the difference between dependence vs addiction?

Dependence refers mainly to physical adaptation whereas addiction involves behavioural compulsivity and priority shift.

Tupper

Researcher who described the historical evolution of the meaning of the term “drug.”