Learning about the Functions of the Olfactory System from People without a Sense of Smell

Abstract

The olfactory system provides numerous functions to humans, influencing ingestive behavior, awareness of environmental hazards and social communication. Approximately ⅕ of the general population exhibit an impaired sense of smell. However, in contrast to the many affected, only few patients complain of their impairment. So how important is it for humans to have an intact sense of smell? Or is it even dispensable, at least in the Western world? To investigate this, we compared 32 patients, who were born without a sense of smell (isolated congenital anosmia - ICA) with 36 age-matched controls. A broad questionnaire was used, containing domains relevant to olfaction in daily life, along with a questionnaire about social relationships and the BDI-questionnaire. ICA-patients differed only slightly from controls in functions of daily life related to olfaction. These differences included enhanced social insecurity, increased risk for depressive symptoms and increased risk for household accidents. In these domains the sense of olfaction seems to play a key role.

Brain structure is changed in congenital anosmia

“…Based on the findings of the present report, one would predict subjects with congenital anosmia to perform differently than controls in according tasks -which is in fact the case, as subjects with congenital anosmia exhibit, for example, significantly higher depression scores compared to normosmic controls (Croy et al, 2012). A meta-analysis linked thickness of the orbitofrontal cortex to depression by showing that subjects suffering from major depressive disorder exhibit thinning of the orbitofrontal cortex (Koolschijn et al, 2009).…”

Olfactory bulb volume predicts therapeutic outcome in major depression disorder

“…Importantly, this is not fully explained by coping problems after loss of a function. People who were born without a sense of smell show a similar enhanced likelihood of depressive symptomatology (Croy et al 2012).…”

Hidden consequences of olfactory dysfunction: a patient report series

“…The social problems that the condition causes for relationships with friends, colleagues, family members, and romantic partners [27,118,119] are partially a consequence of social insecurity caused by worries about undetected body odor and partially a consequence of frustration over the perceived lack of sympathy for the patients [120]. Interactions with medical service providers can also be a source of frustration.…”

“…Smell loss-induced anhedonia is the least-appreciated consequence of smell loss because affected individuals are often not aware of the connection between their olfactory dysfunction and the reduced enjoyment of formerly enjoyable activities. Although the mechanism is unknown, there is a correlation between smell loss and depressive symptoms and mood changes [22,70,115,118,120,122]. …”