We’ve always known that alcoholism is a type of addiction. But figuring out the physical mechanism behind it has been somewhat elusive. Or, at least it was up until now. A team of scientists led by Professor Jianfeng Feng from the University of Warwick found that the physical origin of alcohol addiction is located in the same network of the human brain that regulates our response to danger.
Fight, Flight, Freeze or… Drink?
Whenever the medial orbitofrontal cortex (mOFC) at the front of the brain senses an unpleasant or emergency situation, it relays the information to the dorsal periaqueductal gray (dPAG) at the brain’s core. The dPAG is where our brain processes whether we need to escape the situation.
In the study published in Science Advances, the team found a person is at greater risk of developing alcohol use disorders when the pathway between the mOFC and the dPAG is disrupted. This imbalance can happen in the following two ways:
1. Alcohol inhibits and dulls the dPAG. When this happens, the brain starts having trouble recognizing negative signals. In other words, even when our body and the rest of our brain sends signals of being in danger (of getting drunk, for example), the dPAG can’t register that danger or respond to it by reminding us to stop drinking. The end result is that the alcoholic feels only the benefits of being drunk (feeling good, confident) but subconsciously ignores all the negatives until it’s too late.
2. Alcohol irritates and “excites” the dPAG. Having an over-excited dPAG, gives drinkers the illusion that they are in an adverse or unpleasant situation they wish to escape, and they will urgently turn to alcohol to do so. This is the cause of impulsive drinking.
While these two causes are very different on a biochemical level, their end results are very similar. “We have found that the same neural top-down regulation could malfunction in two completely different ways, yet leading to similar alcohol abuse behaviour,” said Dr Tianye Jia.
The Neural Roots of Alcoholism
The research team had noticed that previous rodent models showed that the mPFC and dPAG brain areas could underlie precursors of alcohol dependence.
They then analyzed MRI brain scans from the IMAGEN dataset — a group of 2000 individuals from the UK, Germany, France and Ireland who take part in scientific research to advance knowledge of how biological, psychological and environmental factors during adolescence may influence brain development and mental health.
The participants undertook task-based functional MRI scans, and when they did not receive rewards in the tasks (which produced negative feelings of punishment), regulation between the mOFC and dPAG was inhibited more highly in participants who had exhibited alcohol abuse.
Equally, in a resting state, participants who demonstrated a more overexcited regulation pathway between the mOFC and dPAG, (leading to feelings of needing urgently to escape a situation), also had increased levels of alcohol abuse.
Alcohol use disorder (AUD) is one of the most common and severe mental illnesses.
According to a WHO report in 2018, more than 3 million deaths every year are related to alcohol use worldwide, and harmful alcohol use contributes to 5.1% of the global burden of disease.
Understanding how alcohol addiction forms in the human brain could lead to more effective interventions to tackle the global problem of alcohol abuse.