Nicotine and Depression

Epidemiological studies indicated that smokers have an increased risk of depression.^i,ii Furthermore, the more they smoke, the greater their risk.ⁱⁱⁱ It is possible that smoking increases depression risk through effects similar to that of caffeine—decreases in cerebral blood flow—even though some depression-related brain messenger chemicals may increase. Older studies indicated that cigarette smoking actually increased cerebral blood flow,^iv but newer research has revealed a much more complicated picture.

For example, in research from Japan,^v Nakamura and colleagues found that after 14 hours of nicotine abstinence, some smokers had increases while others had decreases in brain blood flow. Edward Domino and colleagues at the University of Michigan, Ann Arbor, added further complexity to the nicotine-brain blood flow relationships.^vi They found that nicotine intake in smokers who had been abstinent for 10 hours increased blood flow to some brain areas but decreased blood supply to others. Of concern from the standpoint of depression was a decrease in left-sided brain flow relative to the right in the hippocampal/parahippocampal areas. These areas stimulate the critical orbitomedial prefrontal cortex,^vii and therefore may indicate a nicotine-induced over-dominance of the right frontal lobe—changes that could predispose to depression.

Still other researchers assert that smoking probably does not increase the risk for depression. They claim that the reason nicotine use keeps company with depression is because individuals with depressive tendency tend to medicate themselves with nicotine. Nicotine can raise brain levels of mood-elevating chemicals.^viii

Although the discussions can go back and forth on this subject, several facts remain. First, researchers agree that there is a connection between smoking and depression. Second, no medical practitioner recommends nicotine as a legitimate depression treatment. Therefore, from both the perspective of depression, as well as other nicotine-related brain effects, it is best to leave this addictive chemical out of one’s life