The brain tissue of alcoholics experiences a variety of changes compared to non-alcoholics, according to a new study at the University of Eastern Finland. And while all alcoholics’ brains share some of the same characteristics, the researchers discovered that some changes are exclusive to the brains of anxiety-prone (type I) alcoholics or impulsive (type II) alcoholics.
For the study, the researchers evaluated post-mortem brain tissue from alcoholic persons and non-alcoholic controls. Alcoholics were divided into two groups on the basis of Cloninger’s typology: type I and type II alcoholics.
Type I alcoholics typically develop alcohol dependence later in life and are more prone to anxiety. Type II alcoholics, on the other hand, develop alcohol dependence at a young age and tend to exhibit antisocial behavior and impulsivity.
“From the viewpoint of the study setting, this division was made in order to highlight the wide spectrum of people suffering from alcohol dependence. The reality, of course, is far more diverse, and not every alcoholic fits into one of these categories,” said Olli Kärkkäinen, M.Sc. (Pharm), who presented the results in his doctoral thesis.
One of the changes found in all brains of alcoholics were increased levels of dehydroepiandrosterone, a steroid hormone that affects the central nervous system. These increased levels can, for the most part, explain alcohol tolerance, which develops as a result of long-term use and in which alcohol no longer results in a feeling of pleasure as it once did.
Furthermore, all alcoholics showed decreased levels of serotonin transporters in posterior insula and posterior cingulate cortex, brain regions related to the recognition of feelings and social cognitive processes. This finding could be related to the social anxiety often seen in alcohol-dependent individuals.
The researchers also discovered changes specific to each type of alcoholic. For example, in type I alcoholics, changes were seen in the endocannabinoid system, which modulates stress responses, among other things. Docosahexaenoylethanolamide levels were increased in the amygdala, possibly associated with the anxiety prone nature of type I alcoholics.
On the other hand, brain samples of impulsive, type II alcoholics had increased levels of AMPA receptors in the anterior cingulate cortex. AMPA receptors play a role in the learning and regulation of behavior. This may be associated with the impulsive nature of type II alcoholics.
“These findings enhance our understanding of changes in the brain that make people prone to alcoholism and that are caused by long-term use. Such information is useful for developing new drug therapies for alcoholism, and for targeting existing treatments at patients who will benefit the most,” said Kärkkäinen.
Worldwide, the harm caused by alcohol is estimated to be about as great as the harm caused by the use of all illegal substances combined. In Western countries, approximately 10-15 percent of the population are alcohol-dependent.
The findings are published in the journal Alcohol and Alcoholism, Psychiatry Research: Neuroimaging, and Alcohol.