New research explored whether drinking in adolescence may be linked to alcohol dependence in adulthood, as young people may be especially susceptible to the effects of heavy drinking because their brains are still developing.
"This is the first study in which adolescent RAPI [Rutgers Alcohol Problem Index - a widely-used questionnaire that assesses adolescent drinking-related problems] scores were used to predict later diagnoses of alcoholism," said Richard J. Rose, Professor Emeritus in psychology and brain science at Indiana University, US.
"And it is the first study of pairs of twin brothers and sisters who differ in their RAPI scores to ask whether these co-twins later differ, as expected, in alcohol outcomes. They do."
Adolescents more susceptible
"It might seem silly to even question the existence of a direct pathway from problem drinking to alcohol dependence, in that alcohol dependence is clearly the culmination of an escalating pattern of heavy and problem drinking," noted Matt McGue, a professor in the department of psychology at the University of Minnesota.
"The issue here, though, is whether drinking in adolescence carries particular weight in the development of alcohol dependence in adulthood. That is, adolescents, because of social factors or because their brains are still developing, may be especially susceptible to the effects of heavy drinking."
Rose and his colleagues assessed 597 Finnish twins (300 male, 297 female) at the age of 18 with RAPI, and later interviewed them at age 25 with the Semi-Structured Assessment of the Genetics of Alcoholism to assess alcohol abuse and dependence diagnoses.
"The key finding was that the more drinking-related problems experienced
by an adolescent at age 18, the greater the likelihood that the adolescent would be diagnosed with alcoholism seven years later, at age 25," said Rose.
"That predictive association was stronger in females than males, and was confirmed in within-family comparisons of co-twins who differed in their age 18 RAPI scores. The analysis of co-twins ruled out factors such as parental drinking and household atmosphere as the source of the association, because twins jointly experience these."
"Certainly RAPI is predictive of later risk of alcohol dependence," said McGue. "This means that RAPI can be used to identify a group of late-adolescents who are at high risk for developing alcohol dependence."
However, he added, this may not reflect so much a direct causal effect of adolescent drinking as that individuals who transgress social norms in adolescence by drinking heavily may be those same individuals who transgress social norms in adulthood by drinking abusively.
"In this alternative conceptualisation, the major risk factor is thought to be behavioural disinhibition," said McGue. "The innovation in this study is that the authors were able to confirm the association of adolescent drinking with alcohol dependence within twin pairs. Since twins tend to have similar levels of behavioural disinhibition, showing that the heavily drinking twin was more likely to be alcohol dependent, in part controls for the confounding with behavioural disinhibition.
"Furthermore," he added, "we do not really know why some with high RAPI scores did not become alcohol dependent, and conversely, why some with low scores did. It will be important in future research to investigate whether factors such as behavioural disinhibition can help account for these discrepancies."
Identify elevated risk
Rose said these findings have important implications for clinicians. "The first step in intervention is to identify those at elevated risk," he said.
"Screening for drinking-related problems in adolescence may reliably identify many of those at elevated risk for development of alcoholism, and a self-report instrument such as RAPI offers an efficient approach for such screening. Our results suggest that RAPI is not only an efficient screening assessment; it is an effective one, now shown to be predictive of diagnosed alcohol outcomes."
"While this association may not seem surprising," said Rose, "the strength of the association, in females as well as in males, and in co-twins who differ in drinking, but share their childhood environments and half or all of their segregating genes, was surprising."
"I would say for sure that heavy drinking in adolescence is a real danger sign, regardless of whatever the causal mechanisms are," added McGue. "Heavy drinking in adolescence is an indication that preventive intervention is warranted."
Results were published in Alcoholism: Clinical & Experimental Research. - (EurekAlert!, February 2011)