Alcohol and other drugs can dramatically change our behaviour. Muiris Houston, Medical Correspondent explains why this happens
With a growing concern about people's behaviour under the influence of alcohol and other drugs, what is "the medical and scientific evidence" for their effect on the human psyche and the central nervous system?
Alcohol depresses the activity of nerve cells in the brain. It interferes with the activity of the neurotransmitters GABA and glutamate. The combined effect of this is to dampen down brain activity, especially in the frontal cortex - responsible for our thinking, reasoning and judgment - and the cerebellum, which controls certain aspects of movement. So the first signs of alcohol ingestion are a decline in the clarity of thinking, impaired judgment of situations and distances and a reduced performance in movements which are the results of training, such as balancing or driving.
The familiar effect of alcohol on the brain's higher centres is explained by the cortex's normal function which is to restrain our behaviour and social interactions. As the cortex is depressed by alcohol, these restraints are lost. Some people become more talkative, others are less sexually inhibited. Some become aggressive or violent, as alcohol blocks out normal functioning of the cortex. It seems the particular effect is more a function of the person's personality than something which can be directly attributed to the type or amount of alcohol. And there is some evidence of a genetic susceptibility to alcohol.
Much of the attention on ecstasy has focused on sudden death from single usage and the issue of hydration and a critical rise in body temperature. But the central nervous system effects of MDMA - the medical name for ecstasy - are well documented. It increases the levels of a neurotransmitter in the brain called 5HT, which plays a major role in determining whether we feel depressed or euphoric. People who have taken MDMA describe reduced fear and anxiety, reduced feelings of aggression and a desire for greater intimacy.
Heavy recreational use of ecstasy can cause cumulative damage to the nervous system, causing memory problems and impulsive behaviours. Repeat users are prone to depression, panic attacks and hallucinations.
Animal studies have demonstrated a delayed destruction of the 5HT nerve cells in the brain following the administration of ecstasy, leading to fears that in years to come, humans who have used ecstasy may be prone to Alzheimer's disease type symptoms of mental confusion and changes in sensory perception.
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