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3. BIOBEHAVIOURAL PROCESSES UNDERLYING DEPENDENCE

—a physiological state of withdrawal;
— evidence of tolerance;
—progressive neglect of alternative pleasures or interests;

— persistent use despite clear evidence of overtly harmful consequences.
Compulsive drug-seeking and craving are elicited by the presence of drugs
or associated stimuli (see Chapter 1).
Neuroscience focuses on the events that occur to bring about each of these
symptoms. However, some behaviours are more easily studied than others.
Tolerance and withdrawal have been relatively easier to define and measure
in laboratory animals, which has led to a greater understanding of the effects
of drugs on health and the long-term consequences of substance use.
Concepts such as craving, loss of control and persistent use have been harder
to study in the laboratory. However, modern neuroimaging studies of the
human brain are helping researchers to understand these processes in greater
detail than ever before, and are for the first time giving objective, measurable
images of previously uncharacterizable phenomena such as “craving”.
It is also interesting to relate these biobehavioural learning processes to
the behavioural therapies that are sometimes employed in treating substance
dependence (see Box 3.2). Motivational and cognitive therapies are designed
to work on the same motivational systems in the brain as those that are
affected by substance dependence. These therapies try to replace the
motivation to use drugs with the motivation to engage in other behaviours.
Note that these therapies rely on the same principles of learning and
motivation that are used to describe the development of dependence.
Contingency management, for example, uses the principles of positive
reinforcement and punishment to manage behaviour. Cognitive behavioural
therapies and relapse prevention help the person develop new stimulus–
response associations that do not involve substance use or craving. These
principles are employed in an attempt to “unlearn” the dependence-related
behaviour and to learn more adaptive responses. Similar neurobiological
mechanisms are involved in the development of dependence, as are involved
in learning to overcome dependence.

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