Brain and Nervous System

Immediate effects of alcohol use

Being drunk impairs judgment, inhibitions and concentration, and in increasing amounts leads to drowsiness and coma.[4] The loss of memory for a period of drunkenness (alcoholic blackout) can occur in occasional as well as regular heavy drinkers, and is due to alcohol interfering with the laying down of memories.[4, 8]

Long-term effects of alcohol use

Chronic heavy alcohol use can damage the brain and nerves in a variety of ways. Some damage to the brain, from mild to severe, occurs in around half of chronic heavy alcohol drinkers.[40] This may be due to thiamine (vitamin B1) deficiency (secondary to alcohol use, either because of poor diet or because alcohol reduces the absorption of thiamine from the gut and interferes with how thiamine is used in the body).[41] Thiamine deficiency can cause an acute, severe, life-threatening disorder called Wernicke’s encephalopathy, which usually presents with symptoms of abnormal or paralysed eye movements, difficulty walking and confusion. It also causes a chronic condition of memory loss (variously called Korsakoff’s syndrome, psychosis or dementia), where loss of old memories occurs and difficulties in laying down new memories may be profound.[4, 40, 41] Both of these disorders are ultimately fatal without treatment with thiamine.[4]

Chronic heavy alcohol use can also damage the part of the brain responsible for balance and co-ordination (the cerebellum), leading to instability and problems with walking.[4, 41] It can also damage peripheral nerves in the body, leading to pain, weakness, numbness and the inability to sense touch.[4, 42] In rare cases it can damage specific centres in the brain, leading to loss of mental function, inability to walk and death[8] and can lead to the development of epilepsy (chronic fits) [9] and sleep disturbances. Although individuals suffering from insomnia sometimes use alcohol to treat insomnia, tolerance to the sedating effect of alcohol is likely to occur, increasing the risk of excessive use.[3] Also, if more than one or two drinks are taken in the evening, sleep can be disrupted, increasing the chances of a person waking in the night and finding it hard to fall back asleep.[8]  

The relationship between alcohol use and stroke, where there is a sudden paralysis, loss of sensation or inability to talk because the blood supply to the brain is interrupted, is complex. Alcohol increases the risk of hemorrhagic stroke, where the stroke is caused by bleeding in the brain. However, low to moderate alcohol use (one to two drinks a day) reduces the risk of ischaemic stroke, where the stroke is caused by blockage of the blood vessels in the brain, but higher levels of alcohol use increase the risk of ischaemic stroke.[9]