During adolescence, many people begin to experiment with alcohol, yet relatively little
is known about alcohol’s effects on this critical stage of development. We do know
that early initiation of alcohol use remains one of the most powerful predictors of
later alcohol abuse (Grant 1998). We also know that during adolescence changes occur
in the regions of the brain involved in modulating drug reinforcement, so it cannot
be assumed that factors precipitating alcohol use or abuse are the same in adolescence
as in adulthood. Rapidly changing body systems often are particularly vulnerable to
disruption, and hence long-term consequences may result from alcohol exposure during
this time of accelerated neural and endocrine system maturation (Spear 2000a
). For all of these reasons, adolescence is a critical stage of development, and additional
research is warranted into the effects of drinking during this important transition
period. This sidebar briefly reviews findings on how alcohol affects adolescents,
with a special emphasis on the impact of alcohol on neural and endocrine development.
Though the research in this area is scarce, gender-specific effects are highlighted
Epidemiology of Drinking Among Adolescents
Results from national surveys of adolescents and young adults show that alcohol use
is prevalent among both young men and women. The prevalence of drinking and binge
drinking (consuming five or more drinks on a single occasion in the previous 2 weeks)
is higher among male students relative to their female peers, but data from the Monitoring
the Future Survey (MFS) (Johnston et al. 2002)—a nationally representative sample
of 8th, 10th, and 12th graders—show that the gender gap is closing. For example, in
2001, 36 percent of 12th grade males reported binge drinking, compared with 24 percent
of their female counterparts (a 12-percentage-point difference). However, in 1975
there was a 23-percentage-point difference between rates of male and female binge
drinking (Johnston et al. 2002). Among females, 20.6 percent of 8th graders and 45.1
percent of 12th graders reported using alcohol in the 30 days prior to the survey
(i.e., 30-day prevalence); of those 8th grade females, more than half reported binge
Early Initiation of Alcohol Use
This early alcohol use may have potentially long-lasting consequences. Early onset
of alcohol or other drug use is one of the strongest predictors of later alcohol dependence
(Grant 1998). Although young men are significantly more likely than young women to
report using alcohol before age 13 (34.2 percent versus 24.2 percent) (Grunbaum et
al. 2002), survey data suggest that, over time, the age of initiation to alcohol use
among young women has decreased. For example, in 1975, 42 percent of female high school
seniors reported first using alcohol before 10th grade, compared with 53 percent in
1993 (the last year for which the specific question was asked) (Johnston et al. 2001).
Two possible explanations exist to describe the relationship between early alcohol
use and later dependence. First, exposure to alcohol or other drugs during adolescence
may alter critical ongoing processes of brain development that occur at that time,
increasing the likelihood of problems with alcohol later in life. Indeed, heavy drinking
during early and mid-adolescence has been found to be associated with memory problems
and other neuropsychological deficits, although the causality of this relationship
has yet to be determined (Brown et al. 2000). Another interpretation for the early
exposure effect is that early use of alcohol or other drugs might simply serve as
a marker, not a precursor, for a later abuse disorder. For instance, a preteen’s tendency
to seek out new experiences (i.e., high novelty-seeking behavior) was found to be
predictive of alcohol abuse at age 27 (Cloninger et al. 1988). Strong novelty-seeking
behavior is one of a number of traits that have been linked to early initiation of
alcohol and other drug use (Baumrind 1987).
These two views on the significance of the early exposure effect are not necessarily
mutually exclusive. For example, adolescents with conduct disorder are at higher risk
for early as well as later alcohol and other drug use. Yet people with conduct disorder
who begin to drink at an early age have a particularly high risk for problems with
alcohol and other drugs later in life (Robins and McEvoy 1990).
Neural and Endocrine Development
Striking physical changes occur in the brain during adolescence, including the maturation
of new brain constituents (such as the formation of additional connections between
nerve cells) as well as a prominent loss (or pruning) of some existing connections.
Adolescence-associated changes in the brain’s dopamine (DA) system may affect the
way this important neural messenger communicates with the prefrontal cortex and limbic
brain regions (i.e., the so-called mesocorticolimbic DA system). Changes in these
systems may have a profound effect on adolescent behavior and psychological functioning
). It is possible that features of the adolescent brain may predispose young people
to behave in ways that place them at particular risk for trying alcohol or other drugs.
In rats, the DA system has been implicated in novelty seeking (Dellu et al. 1997)
and has been identified as part of a brain cell circuit involved in assigning value
(i.e., “incentive salience”) to stimuli, including alcohol, and translating the decision
to use alcohol into action (Kalivas et al. 1993).
Adolescence also is the time during which changes in hormone patterns begin to emerge.
Sex differences in behavior appear, orchestrated in part by the rapid changes in these
pubertal hormones (for more information, see the article in this issue by Emanuele
and colleagues, pp. 274–281). Surprisingly, though, puberty-related increases in reproductive
hormones have not been associated in any simple way with other characteristic behavioral
features of adolescence (Susman et al. 1987). Instead, the unique behavioral features
of adolescence—such as a greater emphasis on peer interactions, increased novelty
seeking, and other reckless behavior (Arnett 1992; Spear 2000b
)—may be driven largely by maturational changes in the nervous system, as reviewed
During adolescence, the prefrontal cortex, a region thought to be involved in various
goal-directed behaviors (e.g., rule learning, working memory, and spatial learning)
and in emotional processing (particularly of unpleasant stimuli) undergoes substantial
remodeling. For example, as demonstrated in nonhuman primates, the input from two
key chemicals (i.e., neurotransmitters) involved in brain cell communication—the excitatory
neurotransmitter glutamate and the inhibitory neurotransmitter gamma-aminobutyric
acid (GABA)—is reduced during adolescence, while input from another neurotransmitter,
DA, peaks in the prefrontal cortex during adolescence (Lewis 1997). Another region
that undergoes developmental adjustment is the amygdala (Yurgelun-Todd 1998), a complex
grouping of brain cells that, among other things, is thought to be involved in a person’s
emotional reactions and in coordinating the body’s response to stress.
In research on another brain region, the hippocampus, which is important for learning
and memory, DeBellis and colleagues (2000) used magnetic resonance imaging to evaluate
the volume of this region in alcohol-abusing or alcohol-dependent adolescents (average
age 17). The researchers found that hippocampal volumes were significantly smaller
in the adolescents with alcohol use problems, compared with control subjects. Older
age of onset of the alcohol use disorder and shorter duration of the disorder were
associated with larger hippocampal volume. Although studies show that alcohol use
affects neurocognitive function in adult women and men equally, female study participants’
shorter drinking histories suggest that they may be more sensitive to alcohol’s effects
(Glenn et al. 1988; Nixon 1994). In addition, limited research suggests that women
may be more susceptible than men to alcohol-related brain shrinkage (Hommer et al.
Responses to Stress
Gender differences in the body’s hormonal response to stress also begin to emerge
late in adolescence. For example, compared with males, prepubescent female rats show
elevated levels of corticosterone (analogous to cortisol in humans)—a key stress hormone
(Ramaley and Olson 1974; Cirulli et al. 1996).
In addition, many of the same neural systems known to undergo developmental changes
during adolescence are activated by stress, including DA projections to the pre-frontal
cortex as well as to mesolimbic brain regions (Abercrombie et al. 1989)—areas thought
to be critical in modulating the pleasurable response that follows alcohol use (Koob
1992). In studies with rats, important docking molecules (i.e., receptors) for the
stress hormone corticosterone have been identified on DA cell bodies in the ventral
tegmental area and the substantia nigra as well as in DA terminal regions, including
the nucleus accumbens and the prefrontal cortex (Ahima and Harlan 1990; Cintra et
al. 1994). Increases in corticosterone may play a critical role in activating DA transmission,
as evidenced by the fact that, in rodents, DA levels in the nucleus accumbens (Piazza
et al. 1996) and prefrontal cortex (Imperato et al. 1989) increase with corticosterone
treatment and decrease with removal of the adrenals (the area where corticosterone
is produced). In a similar fashion, adrenalectomy or pharmacologically induced blockade
of stress-hormone synthesis suppresses alcohol consumption in laboratory animals (Fahlke
et al. 1994).
The results of this basic research suggest that stress-induced increases in stress
hormones may interact with mesocorticolimbic brain regions to facilitate alcohol use
behavior. Further research into the effects of stress on the development of alcohol
problems is crucial. Investigations of stress effects in adolescents will be especially
important given the dramatic changes taking place in the brain during that time.
Likewise, further examination of how stress, anxiety, and depression interact in this
age group is important. Adolescence often is characterized as an emotionally stormy
period. Though most children navigate this transitional period without serious problems,
about one-third to one-half of adolescents report significant depressed mood or affective
disturbances that could be described as “inner turmoil” or “feeling miserable” (Compas
et al. 1995; Rutter et al. 1976). Adolescents also tend to show greater extremes in
mood than adults (for a review, see Larson and Richards 1994; Arnett 1999); in addition
to this emotional volatility, anxiety and self-consciousness also appear to peak at
this time (see Buchanan et al. 1992).
Pubertal maturation in girls is associated with emotional difficulties, depression,
and problems with self-image, as well as an increase in risk-taking behaviors (for
a review, see Steinberg and Belsky 1996). During early adolescence, girls may be especially
vulnerable to stress, perceiving events to be more stressful at that time than at
any other (Ge et al. 1994; Wagner and Compas 1990; also see Vik and Brown 1998 for
further discussion of gender differences in perceived stressfulness during adolescence).
This anxiety and stress may play an important part in adolescents’ initiation of alcohol
or other drug use (Pohorecky 1991; Wagner 1993). In her review of the literature on
stress effects on alcohol consumption in humans, Pohorecky (1991) found that stress
clearly influences alcohol consumption in adolescence, but not necessarily in adults.
Indeed, the level of perceived stress was found to be the most powerful predictor
of adolescent alcohol and other drug use, after peer substance use (Wagner 1993).
Researchers need more information about the hormonal, behavioral, and neural interactions
that take place in response to stress during adolescence. Understanding why young
people use alcohol to cope with stress within a developmental timeframe also is important.
The relationship between stress and adult drinking may be far different from the relationship
between these variables in adolescence, the time when most people begin drinking.
Tolerance and Sensitivity to Alcohol’s Effects
Evidence suggests that alcohol may affect adolescents differently than adults. Studies
using animals have shown that, compared with other age groups, adolescents do not
experience the same degree of incoordination and sleepiness when drinking alcohol
as do adults (that is, they are relatively resistant to the motor-impairing and sedative
effects of alcohol) (Silveri and Spear 1998). Adolescents do, however, appear to be
more sensitive to alcohol-induced disruptions in spatial memory (Markwiese et al.
1998). Research is needed to determine when young people in this age group are most
susceptible to alcohol’s effects, what mechanisms underlie this differential age responsiveness,
and whether female adolescents differ from males in alcohol sensitivity at this critical
time. Understanding tolerance and sensitization is particularly important given that
research suggests that a less intense reaction to alcohol may increase the likelihood
that a person will drink more heavily and more often, setting the stage for the development
of alcohol problems (Schuckit 1995).
Research on alcohol’s effects on the developing adolescent is still in its infancy,
despite the fact that this is the time during which many people begin drinking. There
is evidence that people who begin drinking at an early age may have problems with
alcohol later in life. Research also has shown that adolescence is a time when remarkable
changes are taking place in the brain. Just how alcohol use impacts this development
or whether these developmental changes influence alcohol use is unknown.
It also is unclear how gender differences may influence the way that alcohol affects
the developing adolescent brain and other body systems. Researchers have shown that
chronic alcohol consumption can disrupt developmental changes in hormones associated
with puberty in both males (Cicero et al. 1990) and females (Dees et al. 1990). It
also is clear that gender influences the perception of stress, a factor that has been
shown to lead to higher rates of alcohol use among this age group. Just how these
endocrine-related changes influence alcohol use is not fully understood.
Most importantly, future research efforts must examine why early exposure to alcohol
is apparently associated with considerably more adverse consequences than later use,
and why this age group seems at particular risk for alcohol’s deleterious effects.