Understanding Psychology (10th Ed)

 Addictive drugs  produce a physiological or psychological dependence (or both) 
in the user, and withdrawal from them leads to a craving for the drug that, in some 
cases, may be nearly irresistible. In physiological dependence, the body becomes so 
accustomed to functioning in the presence of a drug that it cannot function without 
it. In psychological dependence, people believe that they need the drug to respond to 
the stresses of daily living. Although we generally associate addiction with drugs 
such as heroin, everyday sorts of drugs, such as caffeine (found in coffee) and nic-
otine (found in cigarettes), have addictive aspects as well (Li, Volkow, & Balu, 2007).
We know surprisingly little about the underlying causes of addiction. One of the 
problems in identifying those causes is that different drugs (such as alcohol and 
cocaine) affect the brain in very different ways—yet they may be equally addicting. 
Furthermore, it takes longer to become addicted to some drugs than to others, even 
though the ultimate consequences of addiction may be equally grave (Crombag & 
Robinson, 2004; Nestler & Malenka, 2004; Smart, 2007). 
Why do people take drugs in the fi rst place? There are many reasons, ranging 
from the perceived pleasure of the experience itself, to the escape that a drug-induced 
psychoactive drugs
Drugs that 
infl uence a person’s emotions, 
perceptions, and behavior.
addictive drugs
Drugs that produce 
a biological or psychological depen-
dence in the user so that withdrawal 
from them leads to a craving for the 
drug that, in some cases, may be 
nearly irresistible.
Key Concept
What are the major classifi ca-
tions of drugs, and what are 
their eff ects?
M O D U L E 1 6
Drug Use: The Highs 
and Lows of Consciousness
John Brodhead began to drink heavily 
when he was in the sixth grade.
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