Adolescence is a unique period of neurodevelopment. Nonetheless, the use of alcohol and marijuana is quite prevalent in this period. The advancements in neuroimaging have made it possible to closely analyze the structure and functioning of the brains of adolescent substance users and to identify the circuits where neuropsychological deteriorations are present.
fMRI (functional magnetic resonance imaging) is one of the brain imaging methods used frequently in the studies. fMRI is a method that shows the activation areas of the brain that increase as a response to a mental task and the oxygen levels in the blood, while enabling one to study the neural activity of the brain.
In the studies conducted with fMRI with regard to the influences of the substance use on the brain in adolescents, the adolescents that used substance were found to have abnormalities in their brain functions in association with the neurocognitive functions that changed in time. Abnormalities were observed in the structural volume of the brain, in the quality of the white matter and in the cognitive task activation.
The changes in the brain functions of adolescents vary based on the level of substance use. Nevertheless, abnormalities can be observed even in young people who have an alcohol consumption habit for less than 1-2 years, if there are 20 alcohol consumptions per month and particularly if there is a consumption of more than 4-5 drinks at one sitting.
Studies have shown that an excessive consumption of alcohol during adolescence may lead to low performance in the memory, cognitive tasks, attention, spatial skills and executive functions. These behavioral effects of the excessive consumption of alcohol can occur as a result of the reduction in the volume of important brain structures (e.g. Hippocampus), the quality of the white matter that is at risk, and the abnormalities in the activation during cognitive tasks.
Squeglia, L. M., Jacobus, J., & Tapert, S. F. (2009). The Influence of Substance Use on Adolescent Brain Development. Clinical EEG and Neuroscience, 40(1), 31–38.