4 The Encyclopedia of Addictive Drugs
they crave and are unable to stop taking. Becausedependencehas multiple
meanings, the term is not ideal. However, this book uses the term because of
its familiarity to specialists, despite its potential for causing confusion among
general readers.
The concepts of addiction and dependence differ. Someone who takes a lot
of barbiturates may experience both states. Someone who uses a lot ofmari-
juanamay experience neither. Knowing the differences between those two
concepts can help a person spot confusion in rhetoric about drug abuse.
A person who has dependence on a drug may experience an abstinence or
withdrawal syndrome if the supply runs out. The syndrome may begin several
hours or several days after drug use stops, depending on how long a drug
and its by-products last in the human body. Different drugs have different
withdrawal symptoms, and they are specified in this book’s alphabetical list-
ings. Often a withdrawal symptom is the opposite of what a drug does. For
example, if a drug constipates a person, withdrawal from that drug may in-
clude diarrhea. If a drug makes a person sleepy, withdrawal may include
insomnia. Sometimes the withdrawal syndrome can be avoided if dosage is
gradually reduced rather than stopped suddenly. At times the syndrome is
avoided by substituting another drug that has “cross-tolerance” with the first
one. Cross-tolerance means that one drug can substitute for another in some
ways, typically in ways that prevent a withdrawal syndrome from emerging.
A classic example allowsmethadoneto be substituted forheroin. This book’s
alphabetical section notes cross-tolerance among assorted drugs. Cross-
tolerance is a concept that differs from tolerance described below.
Tolerancemeans that as time passes, a person must use more and more of
a drug to get the same effect. Such an outcome is a traditional sign of addic-
tion. Tolerance can develop to some effects of a drug and not to others. For
example, an amphetamine addict may become tolerant to euphoric properties
of the drug, but not to its poisonous qualities. Acocaineaddict may build
tolerance to appetite-loss properties of the drug but not to other actions. The
opposite may also happen, in which a person becomes sensitized to a drug
and needs less and less. Evidence for such a development has been seen in
humans withDOMand benzodiazepines and in animals withcocaineand
DMT. Such a development, however, would not be considered evidence of
addiction. Tolerance can have a strong mental component; the same phenom-
enon can be seen in reduced pleasure gained from continual indulgence in
wild music events or a particular food or shopping. Recreational and medical
users can take the same drug, often with medical users never developing tol-
erance—perhaps because of the purpose for which they take the drug and not
because of its chemistry, although that possible explanation is not yet con-
firmed. Some experts argue that tolerance is indeed a physical effect, caused
by organic brain changes induced by a drug. Ultimately those experts are
correct: All mental feelings and processes result from changes in the brain’s
electrochemical activity. Some of these changes can even be measured and
correlated with broad psychological characteristics. For example, changes in
brain waves and emotions can be seen after some drugs are administered. Our
understanding of such things remains crude, however. We don’t know how
brain chemicals and electricity induce a person to love someone or hate an