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NEUROSCIENCE OF PSYCHOACTIVE SUBSTANCE USE AND DEPENDENCE

Humans report similar subjective effects from intravenous nicotine as from
smoked tobacco (Henningfield, Miyasato & Jasinski, 1985; Jones, Garrett
&Griffiths, 1999). Craving for tobacco is generally only partially relieved by
the administration of pure forms of nicotine, since it can be elicited by factors
that are not mediated by nicotine (e.g. the smell of smoke, the sight of other
people smoking, and tobacco advertisements), through the process of
conditioning and it can be reduced by constituents in tobacco smoke other
than nicotine, such as “tar” (Butschky et al., 1995). These additional factors
may have synergistic effects with nicotine in cigarettes to provide more
effective relief from craving than nicotine delivered in cigarette smoke (Rose,
Behm & Levin, 1993).

Pharmacological treatment of nicotine dependence
An improved understanding of dependence, and the identification and
acceptance of nicotine as a dependence-producing drug, have been
fundamental to the development of medications and behavioural
treatments for nicotine dependence. There are currently many readily
available treatments to help people reduce their smoking. Estimates are
that over one million people have been successfully treated for nicotine
dependence since the introduction of nicotine gum and the transdermal
patch. All nicotine-replacement therapies are equally effective in helping
people to quit smoking, and, combined with increased public service
announcements in the media about the dangers of smoking, have produced
a marked increase in successful quitting. However, treating dependence
with medication alone is far less effective than when the medication is
coupled with a behavioural treatment. In this case nicotine can prevent the
physical withdrawal effects, while the individual attempts to deal with the
craving and drug-seeking behaviour that have become habitual (see
Chapter 3, section on behavioural therapies). The use of nicotine-based
therapy is not intended for long-term use, but rather only at the beginning
of treatment.
Although the major focus of pharmacological treatments of nicotine
dependence has been nicotine-based, other treatments are being developed
for the relief of symptoms of nicotine withdrawal. For example, the first non-
nicotine prescription drug, the antidepressant bupropion, is currently used
as a pharmacological treatment for nicotine dependence (Sutherland, 2002).
Bupropion improves the abstinence rates of smokers, especially if combined
with nicotine replacement therapy (O´Brien, 2001). Because depression is
frequently associated with nicotine dependence – either by predisposing the
individual to use tobacco, or on account of its development during nicotine
dependence, or as a consequence of nicotine withdrawal – antidepressant
agents have been tested for the treatment of nicotine dependence. This
concept is explored more fully in Chapter 6 where comorbidity of substance
use and mental illness are discussed.

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