Drug addiction is a chronic brain disease – very complex and not just a condition affecting people who lack willpower or are weak of character.
Researchers at the University of Stellenbosch and at UCT, have recently shown through brain imaging of the living brain (those of drug users during and after drug use) the powerful effects of “Tik” (methamphetamine) on the brain’s reward system.
In physiological terms, a drug “high” is experienced when a drug such as tik or cocaine enters the body, and activates the brain’s reward area, causing the nerve cells to suddenly release abnormally large amounts of dopamine, which in turn leads to intense euphoria. This reaction sets in motion a reinforcing pattern that compels the drug user to seek the same “reward” again and again by using more drugs. Eventually the brain adapts to the overwhelming dopamine surges by producing less dopamine or reducing the number of dopamine receptors in the reward area. This translates to reduced enjoyment by the drug user, and therefore more of the drug is needed to get “high” – an effect known as tolerance. Eventually other regions of the brain, besides the reward area are affected, those responsible for judgement, learning and memory. When this happens, drug-seeking behavior becomes driven by habit – and the drug user becomes a drug addict.
It used to be thought that the human brain is fully formed by the age of 12 to 13 years; however, research has shown that the human brain is still developing and maturing during the teenage years, and is only complete at around the age of 25. As Dr S du Plessis from the US points out that adolescents are particularly vulnerable, because receptors in the reward area are extremely sensitive, and with the brain rapidly changing, they are most vulnerable to outside influences and are most likely to experiment with drugs and alcohol during this time of their lives. It also appears that dopamine spikes occur more readily during adolescence in various areas of the developing brain. Such elevated dopamine levels may compel a teenager to seek immediate rewards because the prefrontal cortex, which normally controls such impulses, is not yet fully developed.
The brain imaging studies done by our own South African researchers, supports their hypothesis that dopamine sensitivity renders adolescents susceptible to addiction because drugs, as well as tobacco smoking and alcohol, flood the brain’s reward area with dopamine, triggering intense pleasure and euphoria.
Other types of imaging techniques have also demonstrated biochemical changes in the brain of drug users indicating damage to the health and function of brain cells, including markers of inflammation.
Volkow and others, all researchers working in this field, have found that cocaine, tik, heroin and alcohol all reduce cellular activity in the prefrontal cortex, where strategy rather than impulse decisions are made, and in areas affecting judgment.
All this latest research overwhelmingly demonstrates that drug addiction must be viewed as both a disease of changed brain biology and a behaviour disorder.
Treatment in the future will include both pharmacological and behavioural approaches to addiction. New pharmacological drugs are presently being developed to restore disrupted dopamine function.
Article abbreviated, as appears in “Brain imaging illuminates the impact of addictive drugs on the brain” Tygerland (publication of the Faculty of Medicine and Health Sciences, University of Stellenbosch) November 2012
