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NEUROSCIENCE OF PSYCHOACTIVE SUBSTANCE USE AND DEPENDENCE

The burden of harm to health from psychoactive substance use

No global assessments are available for social harm from substance use (as
shown in Fig. 1.2). However, there is now a developing tradition of estimating
the contribution of alcohol, tobacco and illicit drug use to the global burden
of disease. The first significant attempt at this was in the earlier WHO project
on global burden of disease and injury (Murray & Lopez, 1996). Based on a
standard of measurement known as disability-adjusted life years (DALYs),
estimates of the burden imposed on society due to premature death and years
lived with disability were assessed. The global burden of disease (GBD) project
showed that tobacco and alcohol were major causes of mortality and disability
in developed countries, with the impact of tobacco expected to increase in
other parts of the world.
The reliability of the GBD and other estimates of deaths and disease
depends on the quality of the data they are based upon. Data used in these
analyses were mostly from studies conducted in developed countries
(especially the USA and European countries) and a few, often non-
representative, surveys in developing countries. The inherent difficulty of
assessing the prevalence of substance use and the association between use
and problems also means that the burden estimates were highly approximate.
However, the GBD provided for the first time a set of global data on the burden
of alcohol and other drug use/dependence and there are continuing efforts
to come up with more precise estimates of death and disease burden
associated with licit and illicit substances.
The 2002 World health report (WHO, 2002) includes a new set of estimates
for the year 2000 of the burden attributable to tobacco, alcohol and other
drugs. These estimates are based on data that are significantly more
complete and on more defensible methodologies, and there is no doubt
that they will be improved further in future years. Table 1.4 shows the results
from the estimates for 2000, in terms of the mortality attributable to each
class of substances, as well as a measure of the years of life lost or impaired
due to disability (DALYs). Note that estimated protective effects for heart
disease from moderate drinking have been subtracted to yield the net
negative burden for alcohol (this accounts for the negative number in the
table).
Among the 10 leading risk factors in terms of avoidable burden, tobacco
was fourth and alcohol fifth for 2000, and both remain high on the list in the
projections for 2010 and 2020. The estimated attributable burden in 2000
was 59 million DALYs for tobacco, 58 million for alcohol, and 11 million for
illicit drugs. In other words, tobacco and alcohol accounted for 4.1% and 4.0%,
respectively, of the burden of ill-health in 2000, while illicit drugs accounted
for 0.8%. The burdens attributable to tobacco and alcohol are particularly
acute among males in developed countries (mainly North America and
Europe), where tobacco, alcohol and illicit drugs account for 17.1%, 14.0%
and 2.3%, respectively of the total burden (see Table 1.4).

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