Most of this book is about ‘psychoactive’ drugs. These are substances which have an effect upon the mental state and thereby the mood. Detailed accounts of drug effects are available elsewhere (e.g. Jacobs and Fehr 1987; Plant 1987; Royal College of Psychiatrists 1986). The major types of psychoactive drugs are depressants, stimulants and hallucinogens. Some drugs (such as cannabis) have both depressant and hallucinogenic properties. Others, such as Ecstasy, have both stimulant and hallucinogenic effects. Alcohol is primarily a depressant. It produces a slowing of the rate of activity of the central nervous system, which as with other depressants, may induce a feeling of relaxation. To the drinker the feeling is of increased confidence and enjoyment in social situations, thus the mistaken belief that alcohol is a stimulant. Conversely tobacco, which really is a stimulant, is frequently assumed to be a depressant due to its effect of reducing tension. It is not pejorative to classify alcohol as a ‘drug’. Drugs in themselves are not intrinsically good or bad, legal or illegal. In the public mind the word ‘drug’ is often perceived as referring solely to illicit substances. Such limitation is technically incorrect. Alcohol use is both legal and widely approved in most countries. It is, nevertheless, a drug. As the Royal College of Psychiatrists (1986) has noted, it is ‘Our Favourite Drug’.