Abnormal Psychology

Substance Use Disorders 409

Family and Twin Studies For centuries, observers ranging from novelists to law

enforcement offi cials have noted that members of some families are more likely to

abuse alcohol than are members of other families. In fact, biological offspring of

alcoholics are about twice as likely to become alcoholics as people without such a

family history (Cloninger, Bohman, & Sigvardsson, 1981; Goodwin et al., 1974;

Nurnberger et al., 2004; Russell, 1990).

Twin studies have also provided evidence for a genetic contribution to alcohol-

ism (Cadoret, 1990; Carmelli, Heath, & Robinette, 1993). For example, one study

investigated male twins who had registered with a Swedish Temperance Board be-

cause of problems with alcohol abuse. The results indicated that 54% of the varia-

tion in such abuse could be attributed to genetics and 14% to family environment

(Kendler et al., 1997). Other studies suggest that the genetic infl uence may not be as

high with females (McGue, Pickens, & Svikis, 1992).

Alcoholism and Adoption Studies Sometimes the offspring of alcoholics are

adopted by parents who are not alcoholics, and researchers have studied some of

these children after they’ve become adults. One striking fi nding is that even when they

were raised by nonalcoholic parents, children whose biological parents were alcohol-

ics are much more likely to abuse alcohol as adults than are those whose biological

parents were not alcoholics. Another interesting fi nding from such adoption studies is

evidence that there may be two distinct forms of alcoholism, which arise in part from

different genes (Sigvardsson, Bohman, & Cloninger, 1996). Type 1 alcoholism is less

severe and becomes evident later in life, and the effects of the genes associated with it

can be moderated by environmental factors (such as whether the adoptive father had

a skilled versus an unskilled job). Type 1 alcoholism occurs in both men and women.

In contrast, Type 2 alcoholism apparently emerges early in life and occurs only in

men, and the effects of the genes associated with it outweigh environmental factors.

Some researchers have reported that Type 2 alcoholism arises in males who are (as

were their fathers) impulsive and antisocial (Cloninger, 1987). If further data confi rm

that there are two distinct types of alcoholism, which are affected in different ways by

genes, this would have implications for both diagnosis and treatment. For example,

psychological treatment might be more effective for those with Type 1 alcoholism,

whereas medications might be more important to prevent or treat Type 2 alcoholism.

Alcoholism and Chromosomal Markers Other evidence for the genetic bases of alcohol-

ism comes from studies that link a genetic marker (i.e., a previously identifi ed sequence

of DNA at a particular location on a chromosome), particularly a portion of chromo-

some 11, to the disorder (Blum et al., 1990). But the genetic story is not all negative.

Genes can make an individual more vulnerable to a disorder, but they can also have

the opposite effect: They can protect against alcoholism by making drinking an aver-

sive experience. For example, Asians often have a gene that give them forms of two

liver enzymes that amplify the effects of alcohol (Higuchi et al., 1995),

causing the person to have the negative consequences of drinking (includ-

ing heart palpitations and nausea) after drinking even a little alcohol—

bypassing the pleasant (and reinforcing) sensations that other people

experience with a lower dose of alcohol. Researchers have shown that

(probably because this gene leads alcohol to have larger effects) people

with the gene drink less alcohol (Luczak et al., 2002) and are less likely

to be binge drinkers (Luczak et al., 2001).

However, it is clear that more than one or two genes play a role

in alcohol abuse and dependence; a number of genes, operating to-

gether, infl uence whether a person will develop problems with alco-

hol (Gordis, 1996; Sher, Grekin, & Wilkins, 2005).

Finally, just as we saw for stimulants, neurological factors that

contribute to abuse of and dependence on depressants include activa-

tion of the dopamine reward system, neural-based associations between

drug-related stimuli and drug use, and the role of GABA and glutamate

in shifting recreational drug use to abuse and dependence. Table 9.9

• Increased activity of the GABAnergic system leads to increased
  inhibition of anxiety-related brain structures.


• Depressants indirectly activate the dopamine reward system.


• Depressants generally cause the nervous system to be less
  responsive.


• Some substances directly activate the dopamine reward system,
  including the nucleus accumbens and the ventral tegmental area. *


• Associations between drug-related stimuli and drug use can acti-
  vate the limbic system (and the dopamine reward system).*


• GABA and glutamate are involved in the shift from recreational
  drug use to abuse and dependence.
  This factor is not unique to depressant abuse and dependence.

Table 9.9 • Neurological Factors That

Contribute to the Abuse of and

Dependence on Depressants