Do Some People Smell Their Way Into Depression?

If animals can change their lifestyle in accordance with seasonal variations, why not humans? Well, for one thing, humans don't do things like hibernate, migrate, or breed according to season; or do they? After all, it's pretty well established that inhabitants of warmer, sunnier environments tend to be more erotic. Is that only because the warmer weather leads to less clothing or because there's something about sunlight that tends to be activating? Then again, did I say that humans don't migrate? Don't tell that one to all those snowbirds who empty out New York and flock to Florida in the winter, or their counterparts everywhere else in the world. Well, at least we don't hibernate, that is, unless you take into consideration conditions like seasonal affective disorder, which is now widely known by its aptly abbreviated acronym SAD. This throwback to our primitive nature is accompanied by changes in both mood and behavior. During the fall and/or winter, depression tends to set in. This then tends to dissipate during the spring and summer. There may also be weight gain, diminished sexual appetite, and several other physiologic and behavioral changes reminiscent of hibernation including sleepiness, decreased activity, and decreased social interactions. Sure sounds a lot like a mild form of hibernation, doesn't it?

It now seems that there's more to this SAD story than originally suspected. Researchers working with several mammals observed that removal of the olfactory bulb commonly disrupts seasonal responses to light. Furthermore, when the nerves leading from the nose to the olfactory center in the brain in mice and rats are cut their seasonal response to light disappears. This led Pestolache and his colleagues to investigate what effect the ability to detect odors might have on patients with SAD. Their results were published in the December 2002 Archives of General Psychiatry in an article called "Patients With Seasonal Affective Disorder Have Lower Odor Detection Thresholds Than Control Subjects." The results were statistically significant to a fairly high degree leading to the conclusion that "In humans, marked seasonal behavioral rhythms with recurrent winter depression may be associated with a more acute sense of smell." Sixteen patients with SAD ranging in age from 27 to 66 years were tested during the winter and the following summer using phenyl ethyl alcohol odor detection thresholds. Diagnosis was based on DSM-IV criteria for past major depressive episode. Interestingly, seasonality did not appear to play a role with regard to the ability to smell. Rather, it appears that the main relationship is between depression and olfaction. The increased ability to detect odor remains, even when the depressive state is in remission. No relationship was found with airflow in these patients. The reason for the increase is thought to be due to changes taking place in the orbitofrontal cortex and the amygdala of the brain where there is known to be partial overlap between olfactory and emotional processing. Patients with major depression have been shown, using functional neuroimaging, to probably demonstrate over activity in these regions, thus accounting for over activity of the olfactory sense as well.

The answer to the title question of this article, "Do Some People Smell Their Way Into Depression?" is probably, no. The reason for the coexistence of increased ability to detect odors and SAD is more likely to be an increased activity of two portions of the brain, the amygdala and the orbitofrontal cortex. I, for one, will start observing whether people who complain a great deal about excessive odors also tend to complain about many other things and tend to be depressed. It certainly sounds like something that I've noticed in the past. How about you?

Cartoons and Poems following each article are created and copyrighted by Dr. Ackerman and cannot be copied or reproduced without his permission. Copyright © 2009 by Marvin Ackerman, M.D.