574 Substance-Related and Addictive Disorders
Environmental. Individuals with low incomes and low educational levels are more likely
to initiate tobacco use an d are less likely to stop.
Genetic and physiological. Genetic factors contribute to the onset of tobacco use, the
continuation of tobacco use, and the developm ent of tobacco use disorder, with a degree of
heritability equivalent to that observed with other substance use disorders (i.e., about
50%). Some of this risk is specific to toba cco, and some is common with the vulnerability to
developing any substance use disorder. 
Culture-Related Diagnostic Issues 
Cultures and subcultures vary widely in their acceptance of the use of tobacco. The prev-
alence of tobacco use declined in the United  States from the 1960s through the 1990s, but
this decrease has been less evident in Africa n American and Hispanic populations. Also,
smoking in developing countries is more prev alent than in developed nations. The degree
to which these cultural differences are due to  income, education, and tobacco control ac-
tivities in a country is unclear. Non-Hispan ic white smokers appear to be more likely to
develop tobacco use disorder than are smoker s. Some ethnic differences may be biologi-
cally based. African American males tend to have higher nicotine blood levels for a given
number of cigarettes, and this might contribute  to greater difficulty in quitting. Also, the
speed of nicotine metabolism is significantly different for whites compared with African
Americans and can vary by genotypes associated with ethnicities.
Diagnostic Markers
Carbon monoxide in the breath, and nicotine and its metabolite cotinine in blood, saliva, or
urine, can be used to measure the extent of cu rrent tobacco or nicotine use; however, these
are only weakly related to tobacco use disorder.