Here's why you can't stop smoking after trying so hard

Smoking is a hard habit to break because tobacco contains a chemical called nicotine, which makes it very addictive.

However, every smoker is addicted to a different combination of the “stimulants” in cigarettes, making their personal experience with smoking and nicotine dependence unique. When you first start smoking you may experience nausea, dizziness, headache, or upset stomach, but over time, as your smoking becomes more of a habit, you build up a tolerance to these effects until they become unnoticeable. Tolerance means that it takes more nicotine to get the same effect that we used to get from fewer cigarettes.

Nicotine enters the bloodstream and reaches the brain faster than drugs that enter the body through our veins. Nicotine affects many parts of the body. It changes how the body uses food (metabolism), causes our heart to beat faster, our pulse to quicken, it increases our blood pressure, and our veins begin to tighten causing blood flow throughout the body to become more difficult.

This chemical works by stimulating our nervous system to release specific chemical messengers (hormones and neurotransmitters) that affect different parts of our brain and body. One hormone that nicotine affects is epinephrine, also known as adrenaline. When nicotine is inhaled, the buzz you feel is the release of epinephrine which stimulates the body and causes your blood pressure and heart rate to increase and makes you breathe harder.

Nicotine also activates a specific part of your brain that makes you feel happy by stimulating the release of the hormone dopamine. The release of dopamine when nicotine is inhaled is thought to be the source of the pleasurable sensations you experience when smoking, which can include relaxation, a buzz, and relief of tension.

Once inhaled, nicotine is rapidly distributed throughout the brain within 10 seconds. The enjoyable feelings you experience from smoking occur very quickly, but after you’ve smoked a few times nicotine begins to weaken your ability to feel pleasure, causing you to need more nicotine to sustain the good feelings. This is the cycle of the smoking habit; to continue feeling pleasure from smoking, you must continue to smoke more cigarettes, more frequently.