The first thing to understand when you contemplate quitting smoking is why you are so addicted to it in the first place. Why can’t you just quit?

The reason lies in one of the key components of tobacco: nicotine. Although nicotine contains numerous toxic gases and cancer-causing substances, it is the nicotine that keeps you coming back for more.

Here’s how it works:

Nicotine acts as both a sedative and a stimulant to the central nervous system. As soon as it enters the body – whether from cigarette, cigar, or pipe smoke, or from smokeless tobacco products like “spit” tobacco, chewing tobacco, or snuff – it causes an area of the adrenal cortex (the outer portion of the adrenal gland located on top of each of your kidneys) to release the hormone epinephrine. Epinephrine, which is also known as adrenaline, stimulates the central nervous system and other glands to produce a sudden release of glucose (sugar). This causes the stimulation or “smoker’s high.” But once glucose levels drop – which is usually within 30 minutes of the last cigarette -- depression and fatigue set in, leading the user to crave more nicotine to relieve those symptoms and replace them with the more pleasurable stimulation gained from smoking. It’s a vicious cycle that’s hard to break, but given the health hazards posed by tobacco use, it’s an effort that will pay off in added years—and quality—of life.