Long-term heavy use of alcohol in adolescence alters cortical excitability and functional connectivity in the brain, according to a new study from the University of Eastern Finland and Kuopio University Hospital.
These alterations were observed in physically and mentally healthy but heavy-drinking adolescents, who nevertheless did not fulfill the diagnostic criteria for a substance abuse disorder. The findings were published in Addiction Biology.
The study was part of a larger study known as the Adolescents and Alcohol Study. Researchers analyzed the effects of heavy adolescent drinking on the electrical activity and excitability of the cerebral cortex.
The study did a follow-up on 27 adolescents who had been heavy drinkers throughout their adolescence, as well as on 25 age-matched, gender-matched, and education-matched controls with little or no alcohol use. The participants were 13- to 18-years-old at the beginning of the study. At the age of 23—28, the participants’ brain activity was analyzed using a technique known as trans-cranial magnetic stimulation (TMS), combined with electroencephalogram (EEG) monitoring of brain activity.
In TMS, magnetic pulses are directed at the head to activate nerve cells in the cerebral cortex. These magnetic pulses pass the skull and other tissues, and they are safe and pain-free for the person undergoing TMS.
The method allows for an analysis of how different regions of the cerebral cortex respond to electrical stimulation and what the functional connectivities between the different regions are. Indirectly, the method also makes it possible to analyze chemical transmission and the function of different chemical mediators in the brain. The effects of long-term alcohol use haven’t been studied among adolescents this way before.
The response of nerve cells in the cerebral cortex to the TMS pulse was stronger among alcohol users. They demonstrated greater overall electrical activity in the cerebral cortex, as well as greater activity associated with an important neurotransmitter system. There were also differences between the groups in how this activity spread into the different regions of the brain.
Earlier research has shown that long-term, alcoholism-level use of alcohol alters the function of the neurotransmission system known as GABA. GABA is the most important neurotransmitter inhibiting brain and central nervous system function, and GABA is known to play a role in anxiety, depression, and the development of several neurological disorders.
The study found that alcohol use caused significant alterations in both electrical and chemical neurotransmission among the study participants, although none of them fulfilled the diagnostic criteria of a substance abuse disorder. Moreover, in an earlier study completed at the University of Eastern Finland, also within the Adolescents and Alcohol Study, cortical thinning was observable in young people who had been heavy drinkers throughout their adolescence.
For young people whose brain is still developing, heavy alcohol use is especially detrimental. The findings of the study warrant the question of whether the diagnostic criteria for substance abuse disorders should be tighter for adolescents, and whether they should be more easily referred to treatment. The use of alcohol may be more detrimental to a developing brain than previously thought, although it takes time for alcohol-related adverse effects to manifest in a person’s life.