Recently CNN reported about the most the 5 most addictive drugs. Before I review these drugs I like to briefly describe the dopamine reward system in the brain.
Introduction
The pleasure center consists of the nucleus accumbens, the amygdala and the hippocampus. Together they contain dopamine neurons that communicate with the grey matter nerve cells in the prefrontal cortex. A pleasurable meal, sex, winning a video game, listening to music, earning money and reading a funny cartoon can all cause dopamine release that is perceived as pleasure. But so can drugs, such as smoking cigarettes, drinking alcohol and taking street drugs. The problem is that these latter dopamine releasing substances and drugs cause stronger activation of the dopamine system than natural rewards. But unlike natural rewards they do not cause satiety. This is the basis why drug addiction can kill.
Review of the five most addicting drugs
The neuropsychopharmacologist David Nutt has been part of a committee that decided what the five most addictive drugs are.
Heroin
This is the most addictive drug. It is an opiate that causes the dopaminergic neurons to release up to 200% more dopamine than usual in experimental animals. Heroin is dangerous, because the dose that kills a person is only five times higher than the dose that leads to a high. Most deaths occur because of overdoses.
Cocaine
This drug turns dopamine neurons on, but prevents them from turning the dopamine signal off. In animal experiments cocaine caused the dopamine level to get elevated three times the normal level. 21% of people will become dependent on cocaine sometime during their life when they try it. Methamphetamine, another street drug, is similar to the strength and addictive qualities of cocaine.
Nicotine
When a person smokes a cigarette, the nicotine in it reaches the brain quickly as it is absorbed through the lungs and transported in the blood vessels to the brain. In 2002 there were about 1 billion people on earth who smoked. Every year about 8 million people die from smoking. It was shown in rats that smoking causes dopamine levels in the reward system to rise 25% to 40%.
Barbiturates
This class of drugs also has the name “downers”, because they calm you down and put you to sleep. But they also killed Elvis Presley and Michael Jackson. Both died from an overdose, which suppressed their respiratory center, and they stopped breathing. In low doses barbiturates stimulate the brain and they cause euphoria, but higher doses cause respiratory failure. Nowadays barbiturates are more difficult to get, because physicians prescribe different drugs for insomnia. When a drug is not easily obtainable, it tends to fade in importance in the addiction scene.
Alcohol
In contrast to barbiturates alcohol is readily available. When a person consumes alcohol, the dopamine neurons release between 40% and 360% more dopamine than usual. 22% of people who consume alcohol develop a dependency problem later in life. The WHO estimated that about 2 billion people are addicted to alcohol and 13 million are dying from it every year. The causes of death are varied: car accidents, cirrhosis of the liver, alcohol induced dementia and various cancers.
Dr. Amen’s brain scans
Dr. Amen is a psychiatrist who specializes in SPECT scan technology. SPECT stands for Single Photon Emission Computerized Tomography. This is summarized in this review.
Briefly, a SPECT scan shows where the blood flows in the brain and where it doesn’t flow. People who abuse drugs or nicotine develop areas that have a lack of perfusion. It looks like holes in the brain as depicted under point 5 of the above link, which can create abnormal thinking patterns. Fortunately with drug rehabilitation the brain pattern can normalize again.
The Most Addictive Drugs
Conclusion
The hallmark of drug and nicotine addiction is that the addicted person relies on using a drug to release dopamine from the reward system. Normal pleasures that would do this such as good food, sex or exercise are no longer acceptable to the addicted person. They need drugs, alcohol or nicotine to experience a stronger response. Dr. Amen’s work has shown that this behavior leads to altered brain function with holes visible on SPECT scans (Single Photon Emission Computerized Tomography). Rehabilitation from drug use normalizes the findings on SPECT scans and helps the patient to return to normal functioning.
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About Ray Schilling
