This post is from a quitter that helped so many along the journey when I quit. I have copied his words below. I am quoting Shevie here because I think it may help some of you.
There have been some questions concerning rewards lately. I've been doing research (actually, more like rooting around) into the neuropharmacological aspects of nicotine addiction and thought I'd share a bit here. It's a bit long so if you want the bottom line, just skip to the colored part and start there.
When you experience something pleasurable, certain areas of your brain called reward centers activate by releasing dopamine. The presence of dopamine is what causes the pleasurable feeling, the enjoyment, the �ahhh�.
Smoking causes an increase in the dopamine levels. The actual mechanism is debated, but fMRI studies confirm the increase occurs. As you continue to smoke, the dopamine levels remain high and the brain starts shutting down some of the reward centers in an attempt to return to normal. This causes the smoker to require more, which raises the dopamine levels, which causes the brain to shut down even more reward centers. A balance is eventually reached, typically at the point of a pack per day (about 20 mg of nicotine). This also applies to users of chewing tobacco and snuff.
So now a balance has been reached. The nicotine has raised dopamine levels and the brain has shut down reward centers to compensate. Heroin and cocaine users also reach this maintenance level where the fix no longer causes pleasure, but simply maintains �normal�. When the dopamine level begins to drop (30 � 60 minutes after the last smoke) the smoker begins to feel �the need� and has another fix which re-establishes the dopamine levels.
When the smoker quits the levels of nicotine fall rapidly, as do the dopamine levels. After three to five days the nicotine is out of the system. The brain, however, does not recover as quickly. Without the constant smoking stimulus, dopamine levels are far below where they were. Since reward centers were long ago shut down to compensate for the increased dopamine levels caused by smoking, the (now) ex-smoker is operating at a �reward deficit�. As a result, the ex-smoker feels depressed, ill-tempered, and sad (cries a lot). Those who use sleep as an escape mechanism will tend to sleep much more.
Another effect of this �reward deficit� is that ordinary, everyday rewards don�t seem to work anymore.
[B]My Milage:[/B]
[B]My Quit Date: [/B]7/1/2005
[B]Smoke-Free Days:[/B] 754
[B]Cigarettes Not Smoked:[/B] 15,080
[B]Amount Saved:[/B] $2,639.00
[B]Life Gained:[/B]
[B]Days:[/B] 68 [B]Hrs:[/B] 3 [B]Mins:[/B] 20 [B]Seconds:[/B] 7
