An alcoholic’s brain
Wednesday, 18 September 2013 11:05 Danielle Barron
There is a complex relationship between the brain and alcohol dependence, writes Danielle Barron You can get a heart transplant, a lung transplant, a kidney transplant but you can’t get a brain transplant. The brain remains the final frontier in research as it is still largely unknown territory and full of mystery. What we do know about the brain is that it is remarkably plastic, with the ability to change and adapt to environment and experience over time. Every system, organ and tissue is adversely affected by alcohol misuse but the brain’s role in developing dependence is slowly being elucidated. Professor of Experimental Brain Research at Trinity College Dublin, Prof Shane O’Mara, told IMN that his work has been based on the various connections and physiology involved in the brain’s role in disorders such as alcoholism. “I don’t work on alcoholism directly but what I have had is a longstanding interest in the systems involved in brain plasticity and memory, and, particularly, the brain systems that are affected by one type of alcoholism, which is Wernicke–Korsakoff syndrome,” he said. This syndrome was first described over 100 years now after chronic alcoholics died, and their brains were subsequently found to show marked pathology in the mammillary bodies of the brain. “Interestingly, these people also had very significant amnesia and the link between alcoholism and this part of the brain and amnesia became apparent from this early work over a century ago,” explained Prof O’Mara. “In many senses this is kind of an orphan disease, because with improvements in nutrition you don’t see as many people with this syndrome nowadays. It was originally called a psychosis which is a complete mislabelling because it is much more a neurodegenerative and neuropathological condition.”
Prof O’Mara said that he has been trying to understand the physiology of this part of the brain, and it turns out that that the mammillary bodies are a very complex region of the brain with a very complex role. “What happens in essence, in a disease like Korsakoff syndrome, connectivity between the mammillary bodies and the hippocampus is massively disrupted and gives a very profound and enduring amnesia. Neuroanatomical studies over the last 30-40 years have confirmed the pattern of connectivity in detail, and it appears in alcoholism this loss of connectivity underlies the immense amnesia seen with these patients.”
Understanding how brain plasticity affects clinical disorders such as alcoholism is one thing, but will this new knowledge about the pathophysiological changes that take place in an alcoholic’s brain help in terms of treatments? “Every researcher has hopes for what their research might do when translated to the clinic but the brain really is the great undiscovered and unknown territory so it is hard in one sense to understand how something might be directly translatable, but at the same time you have the hope that increments in knowledge will help to contribute to patient care, at least by helping to fractionate patients into populations that are more treatable than others, or by pointing towards pathways for restitution of function if people can reduce the amount of alcohol that they are consuming,” admitted Prof O’Mara.
It is often said that alcoholism “runs in families”, so how big a role does genetics play in determining one’s risk of developing alcohol dependence? “You have got to be very careful about the genetics here. While there is certainly some data that indicates that alcoholism runs in families, if you have a sibling who is an alcoholic you are much more likely to be an alcoholic or if you have parents that are alcoholic then there is a much better chance that you will be alcoholic. But causality here is the thing, are you drinking because you were exposed to drinking as a normalised behaviour from a very young age or because there is some element of genetic predisposition? We need to be very careful about saying there is anything hard wired in relation to addictive behaviours.” The professor also explained that the influence of one’s environment is probably “much more important” than the genetics in this case, because if someone is never exposed to alcohol they can never, by definition, become an alcoholic. “The focus on culture and context is probably more important than genetics, the effects of which are actually quite limited with small numbers in big populations,” he added. “The argument would be that the brain is not hard wired at all, the brain is in fact remarkably plastic in terms of the environment you are in, the things that you are doing and the substances that you are consuming.” Prof O’Mara referenced recent data from the national Institute for Alcohol Abuse in the US, which illustrated the risk of becoming an alcoholic, depending on the age that someone starts drinking. “What is really marked from the data is that drinking early, at the age of 14 or 15, is associated with a very, very high risk of becoming an alcoholic but if you delay drinking to 18 or 19 the likelihood of becoming an alcoholic is much much lower.” This data points to an important role for the brain plasticity that occurs in the teenage brain, said the professor. “We know that the brain is reorganised substantially during the teenage years because of the development and the hormonal surges that are occurring, and during this window the brain is more vulnerable to insult. For me, that data is both depressing and important. It shows that if you drink early it predicts a lifetime pattern of abuse with much greater probability than genes, but the point is that children who drink as late as possible are going to reduce their risk of alcoholism in later life. This is a much more important story than anything you could say about genetics.” The level of teenage drinking has actually fallen in Ireland in recent years, the latest data shows, added Prof O’Mara. “Central Statistics office data shows that teenage drinking decreased in the period between 2002 and 2010, which is good but the worrying thing is that a quarter of children aged 15 self-reported having been drunk at least once in the last 30 days. That’s very scary but the fraction that reported never having been drunk has gone up and I think that is very very positive.”