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1. INTRODUCTION

CHAPTER 1

Introduction

This report describes our current understanding of the neuroscience of
psychoactive substance use and dependence. It draws on the explosive growth
in knowledge in this area in recent decades, which has transformed our
understanding of the biochemical action of psychoactive substances, and
contributed new insights into why many people use them, and why some
use them to the extent of causing harm or of becoming dependent on them.

Structure of the report
The report is divided into eight chapters. The present introductory chapter is
intended to provide the context and background for the report. Chapter 2
provides a brief overview of basic neuroanatomy, neurobiology and
neurochemistry. Chapter 3 presents the “biobehavioural” view of dependence,
which is based on both learning theory and knowledge of the brain’s functions.
Chapter 4 discusses the pharmacology and behavioural effects of different
classes of psychoactive substances, a branch of science also known as
psychopharmacology. In Chapters 2–4 we consider neurobiological processes
which are to a large extent the common heritage of all human beings. In
Chapter 5, we turn to genetic studies, which focus instead on the
differentiations that may exist between humans in their genetic heritage. The
chapter reviews the evidence for a genetic contribution to substance
dependence, and compares the interaction of genetics and environmental
factors in the development and maintenance of dependence. Chapter 6
considers the neuroscientific evidence on specific interconnections between
substance use and mental disorders, focusing particularly on schizophrenia
and depression. The frame of reference changes again in Chapter 7, which is
concerned with ethical issues in research, treatment and prevention of
substance use disorders, and in particular how these issues may apply to
neuroscientific research and its applications. Chapter 8 deals with the public
health implications of neuroscience research and ends with specific
recommendations for policy.

Psychoactive substances and their sociolegal status

Psychoactive substances, more commonly known as psychoactive drugs, are
substances that, when taken, have the ability to change an individual’s

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