The Effects of Alcohol on Physiological Processes and Biological Development

by National Institute of Health

Adolescence is a period of rapid growth and physical change; a central question is whether consuming alcohol during this stage can disrupt development in ways that have long-term consequences. In general, the existing evidence suggests that adolescents rarely exhibit the more severe chronic disorders associated with alcohol dependence such as liver cirrhosis, hepatitis, gastritis, and pancreatitis. Adolescents who drink heavily, however, may experience some adverse effects on the liver, bone, growth, and endocrine development. Evidence also is mounting, at least in animal models, that early alcohol use may have detrimental effects on the developing brain, perhaps leading to problems with cognition later in life. This article summarizes the physiological effects of alcohol on adolescents, including a look at the long-term behavioral and physiological consequences of early drinking.

The damage that long-term heavy alcohol consumption can do to the health of adults is well documented. Some research suggests that, even over the shorter time frame of adolescence, drinking alcohol can harm the liver, bones, endocrine system, and brain, and interfere with growth. Adolescence is a period of rapid growth and physical change; a central question is whether consuming alcohol during this stage can disrupt development in ways that have long-term consequences.

Liver disease is a common consequence of heavy drinking. More severe alcohol-related liver disease typically reflects years of heavy alcohol use. However, elevated liver enzymes that are markers of harm have been found in adolescents with alcohol use disorders and in overweight adolescents who consume more modest amounts of alcohol.

During puberty, accelerating cascades of growth factors and sex hormones set off sexual maturation, growth in stature and muscle mass, and bone development. Studies in humans have found that alcohol can lower the levels of growth and sex hormones in both adolescent boys and girls. In animals, alcohol has been found to disrupt the interaction between the brain, the pituitary gland (which regulates secretion of sex hormones), and the ovaries, as well as systems within the ovaries that are involved in regulating sex hormones. In adolescent male animals, both short- and long-term alcohol administration suppresses testosterone; alcohol use also alters growth hormone levels, the effects of which differ with age.

Studies on alcohol and adolescent bone development are limited. In studies of male and female rats, chronic alcohol consumption (an alcohol diet) for the length of adolescence was found to stunt limb growth. One study found that feeding female rats alcohol in a way that mimics binge drinking resulted in either increases in bone length and density or in no change with more frequent bingeing. In human adolescent males but not females, studies have found that alcohol consumption decreases bone density.

The brain also is changing during adolescence. Adolescents tend to drink larger quantities on each drinking occasion than adults; this may in part be because adolescents are less sensitive to some of the unpleasant effects of intoxication. However, research suggests that adolescents may be more sensitive to some of alcohol's harmful effects on brain function. Studies in rats found that alcohol impairs the ability of adolescent animals more than adult animals to learn a task that requires spatial memory. Research also suggests a mechanism for this effect; in adolescents more than adults, alcohol inhibits the process in which, with repeated experience, nerve impulses travel more easily across the gap between nerve cells involved in the task being learned. The reasons for these differences in sensitivity to alcohol remain unclear.

Research also has found differences in the effects of bingelike drinking in adolescents compared with adults. Normally, as people age from adolescence to adulthood, they become more sensitive to alcohol's effects on motor coordination. In one study, however, adolescent rats exposed to intermittent alcohol never developed this increased sensitivity. Other studies in both human subjects and animals suggest that the adolescent brain may be more vulnerable than the adult brain to chronic alcohol abuse.

Young people who reported beginning to drink at age 14 or younger also were four times more likely to report meeting the criteria for alcohol dependence at some point in their lives than were those who began drinking after age 21. Although it is possible that early alcohol use may be a marker for those who are at risk for alcohol disorders, an important question is whether early alcohol exposure may alter neurodevelopment in a way that increases risk of later abuse. Research in rats has found that prenatal or early postnatal exposure to alcohol results in a greater preference for the odor and consumption of alcohol later in life. Social experiences associated with youthful drinking also may influence drinking later in life. Additional research is needed to resolve the question of whether and how early alcohol exposure might contribute to drinking problems years down the road.

Alcohol's Effects on the Liver, The Neuroendocrine System and Bone

The medical consequences of chronic alcohol abuse and dependence have been well documented in adults. They include liver disease, lung disease, compromised immune function, endocrine disorders, and brain changes. Investigations of the health problems associated with adolescent alcohol abuse are sparse and rely mainly on self-report. In general, the existing evidence suggests that adolescents rarely exhibit the more severe chronic disorders associated with alcohol dependence, such as liver cirrhosis, hepatitis, gastritis, and pancreatitis. However, more research is needed to determine whether severe alcohol-induced organ damage is strictly a cumulative process that begins in adolescence and culminates in adulthood as a result of long-term chronic heavy drinking or whether serious alcohol-related health problems can emerge during the teenage years. The few studies available indicate that adolescents who drink heavily experience adverse effects on the liver, bones, growth, and endocrine development, as summarized below. The effects of chronic alcohol consumption on the adolescent brain are discussed in the section "Long-Term Behavioral and Physiological Conse quences of Early Drinking."

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.