Addiction Medicine: Closing the Gap between Science and Practice

addiction.* 47 Adopted children with biological
parents who have addiction involving alcohol
are at least twice as likely as are adopted
children without such parents to develop
addiction involving alcohol.^48 Individuals
whose genetic makeup produces involuntary
skin flushing and other unpleasant reactions to
alcohol are at reduced risk of developing
addiction involving alcohol.^49

Other Drugs. Genetic influences have been
implicated in marijuana use^51 and particular
genes have been associated with marijuana
cravings and withdrawal symptoms.^52 Twin
studies have found genetic risks for
hallucinogen, opioid, sedative and stimulant use
and addiction.^53

Biological Risks ...........................................................................................................

In addition to genetic variations, certain
individuals have neurological, structural or
functional differences that make them more
susceptible to addictive substances.^54 This is in
part due to individual differences in how the
brain produces and reacts to dopamine.^55 Some
research indicates that individuals with a
naturally low level of dopamine response to
addictive substances are at increased risk of
engaging in substance use in order to achieve a
greater experience of reward. Other research
suggests that individuals with a biological

• There is some indication that these individuals have

less cognitive impairment following the ingestion of
alcohol and, therefore, may not perceive the negative
experiential aspects of alcohol use in the same
manner as individuals whose brains are more strongly
affected by alcohol ingestion.

tendency toward heightened dopamine response

also are at increased risk because of their

enhanced or above average experience of reward

or pleasure from engaging in substance use.^56

Other biological risks may involve damage or

deficits in the regions of the brain† responsible

for decision making and impulse control.^57

Psychological Risks .....................................................................................................

Clinical mental health disorders such as

depression and anxiety and psychotic disorders

such as schizophrenia, as well as behavioral

disorders such as conduct disorder and attention-

deficit/hyperactivity disorder^58 --and sub-clinical

symptoms of these conditions^59 --are strongly

linked to substance use and addiction and to the

risk of transitioning from substance use to

addiction.^60 Individuals whose brain

development has been altered by stress are more

sensitive to the effects of addictive substances

and more vulnerable to the development of

addiction.^61 Likewise, individuals with post-

traumatic stress disorder (PTSD), common

among veterans and individuals in active

military duty, are at increased risk of developing

addiction.^62 People who have risk-taking or

impulsive personality traits^63 or who have low

self-esteem^64 also are likelier to engage in

substance use^65 as are victims of trauma or

abuse.^66 Expectations play a role in substance

use as well, since people who expect that using

addictive substances will be a positive and

rewarding experience--in terms of physical

effects, mood or behavior--are likelier to smoke,

drink alcohol or use other drugs than are those

with more balanced or negative expectations.^67

Environmental Risks ....................................................................................................

Many factors within an individual’s family,

social circle and community, as well as the

larger cultural climate, increase the likelihood

that an individual will use addictive substances

and develop addiction.

† e.g., in the orbitofrontal cortex and anterior

cingulate cortex.

It’s theoretically possible to take kids before

they first drink, find out whether they have any

gene variations, and say to them, ‘If you choose

to be a drinker, then be careful because it’s very

likely that you’ll need to drink more to have the

same effect.’^50

--Marc A. Schuckit, MD

Distinguished Professor of Psychiatry

Department of Psychiatry

University of California, San Diego