Nicotine is an alkaloid found in the nightshade family of plants; nightshade of course is poisonous to humans. It acts as a stimulant and is the main reason why smokers become addicted to cigarettes – there is actually a “high” that’s experienced when one smokes because of the nicotine.

According to the American Heart Association, "Nicotine addiction has historically been one of the hardest addictions to break." The pharmacological and behavioral characteristics that determine tobacco addiction are similar to those that determine addiction to drugs such as heroin and cocaine.

Nicotine in small doses acts as a stimulant to the brain. In large doses, it’s a depressant, inhibiting the flow of signals between nerve cells. In even larger doses, it’s a lethal poison, affecting the heart, blood vessels, and hormones. Nicotine in the bloodstream acts to make the smoker feel calm.

Nicotine is extremely dangerous because of how quickly it’s absorbed in the bloodstream. As nicotine enters the body, it is distributed quickly through the bloodstream and can cross the blood-brain barrier. On average it takes about seven seconds for the substance to reach the brain when inhaled. Nicotine causes an adrenaline rush, and affects the heart rate, blood pressure, and pulse of its users.

Nicotine’s mood-altering effects are also well documented. After the initial adrenaline rush, users report a feeling of relaxation and calm. It then reduces the appetite and raises the metabolism, causing some to lose weight when smoking, another reason why they become hooked.

However, all of these properties of nicotine are similar to the properties of many illegal narcotics. There is no health benefit to nicotine regardless of the feelings it produces in the user. The so-called “high” one experiences is artificial and temporary.

Additionally, the addictive properties of nicotine are extremely dangerous. Modern research shows that nicotine acts on the brain to produce a number of effects. Specifically, its addictive nature has been found to show that nicotine activates reward pathways—the circuitry within the brain that regulates feelings of pleasure and euphoria.

By “rewarding” the user, nicotine then makes them addicted to this feeling or sensation. That temporary high creates a craving for that experience again, much like someone coming down from the high of any other illegal narcotic. The brain’s ability to produce these reward pathways on its own is compromised each time it is created in an artificial way, causing the user to become hooked on that artificial substance.