'Scratch and sniff' test sheds light on depression

A five-minute test commonly used to evaluate olfactory function (sense of smell) could also help doctors screen for depression, according to new research out of King George's Medical University, India. The research was presented at the American Physiology Summit, held in Long Beach, California, April 20–23.

According to the World Health Organization, depression is a leading cause of disability, affecting 1 in 20 adults around the globe. There is a known correlation between loss of smell and depression, often assessed by comparing depression diagnosis with the results of the University of Pennsylvania Smell Identification Test (UPSIT).

The UPSIT is a commercially available, standardized and trusted screening tool of 40 scratch-and-sniff samples that require the user to identify scents using corresponding multiple-choice questions. The Brief Smell Identification Test (B-SIT) is a rapid version of the UPSIT that uses 12 smells instead of 40. Identifying eight or fewer smells on the B-SIT is considered abnormal.

The current study screened 35 people diagnosed with depression and 32 age- and sex-matched healthy controls. All the members of the depression group identified fewer smells than the control group. Twenty-seven participants in the depression group scored below the cutoff score of eight. Participants with recurrent depressive episodes had a mean BSIT score of 5.20.

"To our surprise, we found that the degree of olfactory dysfunction was directly proportional to the severity of depression," said lead study author Manish Bajpai, MD.

"The easy and rapidity of the B-SIT could make a useful addition to clinical screening," the researchers wrote.