The 5 most addictive substances on Earth are heroin, alcohol, cocaine, barbiturates, and nicotine. These substances are addictive because of how it affects the brain’s dopamine system, creates pleasurable experiences and promotes cravings and increased tolerance. They are also addictive because they are not easy to stop using and have serious withdrawal symptoms. Heroin ranks as the most addictive drug in the world with a 2.5/3 score. It can cause death if a dose 5 times greater than the dose for a high is taken. Alcohol scores a 2.2/3 making it the second most addictive substance because 22% of those who drink alcohol end up addicted and in 2012, over 3 million have died from alcohol-related circumstances. Crack cocaine comes in at third place while powder cocaine comes in at fifth place. Cocaine can cause dopamine levels to rise up to 3 times the normal level. Estimates are that up to 20 million people take cocaine. Barbiturates is ranked 4th most addictive substance and is used to treat anxiety and insomnia. At high doses, they are lethal and can stop a person from breathing. Finally, nicotine comes in at fifth place along with powdered cocaine. Nicotine is the addictive ingredient in tobacco products. There are over a billion people addicted to nicotine and by 2030 around 8 million will be dying annually from this addiction.