Alcohol, Adolescents, and Adults (citations)

Original
A concern amongst neuroscientists today who study alcohol and the brain is how the many effects of alcohol differ between ages, specifically between adolescents and adults. For clarification, adolescence is oftentimes defined as the second decade of life, but neurologically it extends until the age of 25.1 Thus, when researchers discuss the effects of alcohol on adolescents they are not speaking strictly of teenagers but of a broad group that extends from middle school students to young adults. Since it is unethical to supply alcohol to those below the drinking age in a laboratory setting researchers are forced to use rats for experimental trials.

Short-term effects
In various experiments performed on laboratory rats, the adolescent brain shows levels of greater impairment than the adult brain when it comes to memory retrieval and imprinting capabilities than the adult brain.2 This is to say that the adolescent brain is worse at remembering things while drunk, and remembering things that happened while drunk. Interestingly though, when it comes to motor skills, the adolescent brain maintains a higher level of balance, reaction time, and hand eye coordination while under the same level of intoxication as an adult brain.3

Long-term effects
Concerning long-term effects, evidence from rat lab experiments indicate that repeated exposure to large amounts of alcohol during adolescence leads to long lasting deficits in cognitive abilities, including learning and memory.4 In rats these deficits are more pronounced in adolescents than in adults.5 Results from human studies are less clear. Brain imaging and behavioral measurements of the brain in young adolescents that are heavy drinkers show lower rates of brain activity during memory tasks and less developed brain structures than in their non-drinking peers.6 While those results are troubling, they are consistent with findings from older, adult subjects.7 In the only study that to our knowledge that compares drinkers who started drinking either after 21 or before 21, but still controls for years of drinking and quantity of consumption, researchers found the two groups to be indistinguishable in terms of long-term cognitive impairments.8 Thus, the cognitive deficits attributed to alcohol use during adolescence are indicative not of alcohol’s unique effect during that stage of development, but of the consequence heavy alcohol use has more generally.

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1 Spear, L.P. (2000). The adolescent brain and age-related behavioral manifestations. Neuroscience and Biobehavioral Review, 24, 417-463.

2 White, A.M. & Swartzwelder, H.S. (2004). Hippocampal function during adolescence: A unique target of ethanol effects. New Annals of the New York Academy of Sciences, 1021, 206-220.

3 White, A.M., Truesdale, M.C., Bae, J.G., Ahmad, S., Wilson, W.A., Best, P.J. & Swartzwelder, H.S. (2002). Differential effects of ethanol on motor coordination in adolescent and adult rats. Pharmacology, Biochemistry and Behavior, 73,673-677.

4 White, A.M., Bae, J.G., Truesdale, M.C., Ahmad, S., Wilson, W.A. & Swartzwelder, H.S. (2002). Chronic-intermittent ethanol exposure during adolescence prevents normal developmental changes in sensitivity to ethanol-induced motor impairment. Alcoholism: Clinical and Experimental Research, 26(7), 960-968.

5 White, A.M., Ghia, A.J., Levin, E.D. & Swartzwelder, H.S. (2000) Binge pattern ethanol exposure in adolescent and adult rats: Differential impact on subsequent responsiveness to ethanol. Alcoholism: Clinical and Experimental Research, 24(8), 1251-1256.

6 Brown, S.A. & Tapert S.F. (2004). Adolescence and the trajectory of alcohol use: Basic to clinical studies. Annals of the New York Academy of Sciences, 1021, 234-244.

7 Pfefferbaum A., Sullivan E.V., Rosenbloom M.J., Mathalon D.H. & Lim K.O. (1998). A controlled study of cortical gray matter and ventricular changes in alcoholic men over a 5-year interval. Archives of General Psychiatry, 55(10), 905–912; Hommer, D.W., Momenan, R., Kaiser, E. & Rawlings, R.R. (2001). Evidence for a gender-related effect of alcoholism on brain volumes. The American Journal of Psychiatry, 158(2), 198-204; Sullivan, E.V., Marsh, L., Mathalon, D.H., Lim, K.O. & Pfefferbaum, A. (1995). Anterior hippocampal volume deficits in nonamnesic, aging chronic alcoholics. Alcoholism: Clinical and Experimental Research, 19(1), 110-122; Moselhy, H.F., Georgiou, G. & Khan, A. (2001). Frontal lobe changes in alcoholism: A review of the literature. Alcohol & Alcoholism, 36(5), 357-368.

8 Demir, B. Ulug, B. Lay Ergun, E. & Erbas, B. (2002). Regional cerebral blood flow and neuropsychological functioning in early and late onset alcoholism. Psychiatry Research, 115(3), 115-125.