Page 231 - Pagetit

NEUROSCIENCE OF PSYCHOACTIVE SUBSTANCE USE AND DEPENDENCE

Lindblad & Vinnerljung, 2002), twin studies of the genetics of substance
dependence (Heath, 1995) and longitudinal studies of substance use and its
consequences (Fergusson & Horwood, 2000; Kandel & Chen, 2000) and among
persons who have been treated for substance dependence (Hser et al., 2001).
The findings of such studies inform neuroscience research by describing
substance dependence phenomena that need to be explained by
neuroscience theories, for example, the individual characteristics that predict
substance use and the development of substance dependence and other
drug-related problems, and the genetic epidemiology of substance
dependence found in twin and adoption studies. The distinction between
epidemiological and neuroscience research on substance dependence is also
likely to become blurred when epidemiological studies include biological
measures, such as DNA, from which specific susceptibility genes can be
tested, as well as other biological markers of risk.

Experimental studies in humans
Human neuroscience experiments typically involve laboratory studies under
controlled conditions of the effects of chronic drug exposure on current brain
function or the acute effects of exposure to drugs, drug analogues, or drug-
related cues (e.g. the presence of injecting equipment) on behaviour and brain
function (Adler, 1995). An increasingly common type of study involves the
use of brain imaging technologies, such as PET, SPECT and fMRI (Gilman,
1998; Fu & McGuire, 1999) to study the acute effects of drugs and the
neurobiological consequences of chronic substance use and dependence (Sell
et al., 1999; Kling et al., 2000; Martin-Soelch et al., 2001) (see Chapters 2 and 4).

Clinical trials of pharmacotherapy for substance dependence
Clinical trials of pharmacotherapies for substance dependence compare the
effects of different drug treatments, and sometimes placebos, on the patterns
of drug use, on health, social adjustment and well-being of persons who are
dependent on drugs (Brody, 1998). The drugs that are trialed are increasingly
identified as potential treatments for substance dependence as a result of
neuroscience research on the biological mechanisms underlying substance
dependence. These may include trials of drugs that assist in completing the
withdrawal from a psychoactive substance; drugs that are intended to reduce
relapse to substance dependence after withdrawal; and drugs that are
intended to provide long-term maintenance of abstinence or psychosocial
stability.
Clinical trials have some chance of benefiting participants in the study
(Brody, 1998). This may be by obtaining access to good-quality treatment
for substance dependence (in the event of their receiving standard
treatment or a placebo) or access to a promising experimental treatment
for substance dependence (if they are assigned to the new treatment). As

210

Chapter_7 210 19.1.2004, 11:50