Immediate and Rapid Effects on the Brain

Part of the addictive power of nicotine comes from its direct effect on the brain.  In addition to the well understood chemical dependency, cigarette smokers also show evidence of a higher rate of behavioral 

problems and suffer the following immediate effects: 

• Increases Stress.  Contrary to popular belief, smoking does not relieve stress.  Studies have shown 

that on average, smokers have higher levels of stress than non-smokers. The feelings of relaxation 

that smokers experience while they are smoking are actually a return to the normal unstressed state 

that non-smokers experience all of the time.

• Alters brain chemistry.  When compared to non-smokers, smokers brain cells- specifically brain cell 

receptors- have been shown to have fewer dopamine receptors.  Brain cell receptors are molecules 

that sit on the outside of the cell interacting with the molecules that fit into the receptor, much like a 

lock and key.  Receptors (locks) are important because they guard and mediate the functions of the 

cell.  For instance when the right molecule (key) comes along it unlocks the receptor, setting off a 

chain of events to perform a specific cell function.  Specific receptors mediate different cell activities.   

Smokers have fewer dopamine receptors, a specific cell receptor found in the brain that is believed to

play a role in addiction. Dopamine is normally released naturally while engaging in certain 

behaviors like eating, drinking and copulation. The release of dopamine is believed to give one a

sense of reward.  One of the leading hypothesis regarding the mechanism of addiction theorizes that 

nicotine exposure initially increases dopamine transmission, but subsequently decreases dopamine 

receptor function and number.  The initial increase in dopamine activity from nicotine results initially in 

pleasant feelings for the smoker, but the subsequent decrease in dopamine leaves the smoker 

craving more cigarettes.

             New animal studies have shown that brain chemistry and receptors may be altered early in the 

smoking process. Habitual smoking may continue to change brain chemistry, including decreasing 

dopamine receptors and thus yielding a more intense craving and risk of addiction.  These brain 

chemistry changes may be permanent.  In addition, because the role played by receptors in other 

cognitive functions, such as memory and intelligence, is unknown, how cigarette smoking effects.