BROADCASTS.com

https://slatestarcodex.com/2020/04/17/depression-the-olfactory-perspective/

\xa0

Depressed people have worse sense of smell, and people with worse sense of smell are more likely to get depressed.\xa0Kohli 2016\xa0tries to figure out what\u2019s going on.

They review six studies testing how well depressed people can smell things. Most use something called \u201cThe Sniffin\u2019 Sticks Test\u201d (really!) where people are asked to say which of two sticks has an odor; the strength of the odorous one is then decreased until the subject can no longer consistently get it right. This determines olfactory threshold \u2013 how sensitive the subject\u2019s smell is. Depressed subjects did marginally (but significantly) worse on this test than controls (6.31 \xb1 1.38 vs. 6.78 \xb1 0.88; P = 0.0005) \u2013 I think this corresponds to an effect size of about 0.2. They also do a couple more tests to see if depressed people are worse at identifying odors and get similarly small results. Also, some\xa0neuroimaging studies\xa0directly correlate depression and olfactory bulb volume, and find that olfactory areas of depressed people\u2019s brains shrink.