Drugs, Brains, and Behaviour: The Science of Addiction
As a result of scientific research, we know that addiction is a disease that affects both brain and behaviour. Drugs are chemicals. They work in the brain by tapping into the brain’s communication system and interfering with the way nerve cells normally send, receive, and process information.
Some drugs, such as marijuana and heroin, can activate neurons because their chemical structure mimics that of a natural neurotransmitter. This similarity in structure “fools” receptors and allows the drugs to lock onto and activate the nerve cells.
Although these drugs mimic brain chemicals, they don’t activate nerve cells in the same way as a natural neurotransmitter, and they lead to abnormal messages being transmitted through the network.
Other drugs, such as amphetamine or cocaine, can cause the nerve cells to release abnormally large amounts of natural neurotransmitters or prevent the normal recycling of these brain chemicals.
This disruption produces a greatly amplified message, ultimately disrupting communication channels. The difference in effect can be described as the difference between someone whispering into your ear and someone shouting into a microphone.
When some drugs of abuse are taken, they can release 2 to 10 times the amount of dopamine that natural rewards do.
In some cases, this occurs almost immediately (as when drugs are smoked or injected), and the effects can last much longer than those produced by natural rewards. The resulting effects on the brain’s pleasure circuit dwarfs those produced by naturally rewarding behaviours such as eating and sex.
The effect of such a powerful reward strongly motivates people to take drugs again and again. This is why scientists sometimes say that drug abuse is something we learn to do very, very well.