Alcohol use in adolescence: A longitudinal study of its effect on cognitive functioning

It has been suggested that the adolescent brain is particularly vulnerable to the neurotoxic effects of alcohol because significant maturation of brain structure and corresponding cognitive control function takes place over the course of adolescence. However, research on this subject has remained inconclusive thus far due to numerous methodological pitfalls. Therefore, there is a need for a large longitudinal study on the precursors and outcomes of alcohol use related to cognitive and behavioural control. The main aim of the present thesis was to longitudinally investigate the effect of alcohol use in adolescence on cognitive functioning. To address this research question adequately, we first studied normal maturation of cognitive control. Next, answering the main research question, we assessed whether deviances from this normal maturation where found among heavy drinkers and adolescents with alcohol use disorder (AUD; adolescents who meet the criteria for alcohol abuse and alcohol dependence. ). Furthermore, we assessed cognitive and behavioural control as precursors of alcohol use in order to identify adolescents at risk for transitioning to heavy drinking and AUD.
Cognitive control was found to mature significantly over the course of adolescence. However, no differences in this maturation were found between drinking and non-drinking adolescents, suggesting that heavy drinkers and alcohol abusers may not be at risk for a deviant maturation of such functions. Only the small and specific group of female alcohol dependents showed a distinct maturation of shift attention, but it is unclear whether this distinct maturational pattern reflects permanent irreversible damage. Nevertheless, heavy drinking and, more pronounced, AUD is prospectively related to increases in problematic behaviour reflecting diminished behavioural control. This implicates that even when the cognitive ‘hardware’ for being able to control and direct behaviour is intact, that is, cognitive control functions, actual behavioural control can be suboptimal, leading to adverse outcomes, such as heavy drinking and AUD. The present thesis is the first large longitudinal study on the effects of alcohol use in adolescence on cognitive functioning. It contributes to more insight into the complex reciprocal relationship between adolescent alcohol use with cognitive and behavioural control while simultaneously underlining the fact that much more research is necessary. No evidence for vast cognitive deficits as a result of alcohol use was found, and findings from this thesis indicate that the effects of alcohol on the developing brain might more subtle than has been assumed thus far. More research is needed to understand what influence alcohol has on the developing brain and how this would affect functioning in daily life.