Summary: Women with postpartum depression show normal basic smell detection but altered perception of scent intensity and pleasantness, while people with a genetic predisposition to major depressive disorder often show reduced olfactory sensitivity.
Source: University of Otago
New research from the University of Otago indicates that women experiencing postpartum depression perceive smells differently from healthy mothers, reinforcing the view that postpartum depression may differ from major depressive disorder in important sensory and neurobiological ways.
Dr Mei Peng, lead author and researcher in the Department of Food Science, explains that the study’s findings support emerging evidence that postpartum depression (PPD) should be considered and studied separately from generic major depression. “Postpartum depression has long been treated as a subtype of major depressive disorder, despite low diagnostic rates and many women remaining undiagnosed and untreated. Recent work suggests that the disorders affect the brain differently, and our study provides sensory evidence consistent with that distinction,” she says.
Pregnancy-related depression is common: estimates suggest 6–12 percent of women are affected during pregnancy and more than 20 percent after childbirth. Clarifying whether PPD is distinct from other depressive conditions has direct consequences for diagnosis, treatment strategies, health policy, and future research priorities.
This multidisciplinary, world-first study—published in Scientific Reports—evaluated olfactory function in 39 mothers within the perinatal period (during pregnancy up to one year after giving birth) who were assessed using the Edinburgh Postnatal Depression Scale. The depressed group was compared with a case-matched healthy control group. Each participant completed two testing sessions spaced four weeks apart, including a standardized odor detection threshold test and ratings of intensity and pleasantness (valence) for a set of six odorants (three typically rated as pleasant and three as unpleasant).
The primary result showed no meaningful difference in odor detection thresholds between the depressed and control groups (patients: mean 5.6, SE 0.3; controls: mean 5.7, SE 0.4), indicating that early-stage olfactory processing—the ability to detect odors—remains intact in PPD. However, mothers with postpartum depression rated the three unpleasant odorants as significantly less pleasant and perceived two of the test odorants (one pleasant, one unpleasant) as less intense. These perceptual differences did not appear to be substantially affected by the participant’s specific perinatal stage.
Dr Peng and colleagues interpret these findings to mean that postpartum depression is linked to changes in higher-order olfactory processing—how the brain evaluates and assigns hedonic value and intensity to smells—rather than to changes in basic odor detection. In contrast, previous work has found reduced olfactory sensitivity in people genetically predisposed to major depressive disorder, highlighting a potential sensory distinction between PPD and other forms of depression.
The study’s authors emphasize that sensory symptoms are an underexplored feature of postpartum depression. Greater attention to olfactory and other sensory changes could improve understanding of PPD’s neurobiology, assist in the development of better diagnostic tools, and inform tailored treatment approaches that address the specific perceptual and emotional experiences of affected women.
The research team is seeking funding to expand this line of inquiry and to investigate how pregnancy and the postpartum period may influence women’s long-term quality of life through sensory and other neurobiological changes.
About this depression research news
Source: University of Otago
Contact: Mei Peng – University of Otago
Image: The image is in the public domain
Original Research: Open access. “Olfactory shifts linked to postpartum depression” by Mei Peng, Hazel Potterton, Joanna Ting Wai Chu & Paul Glue. Scientific Reports
Abstract
Olfactory shifts linked to postpartum depression
Postpartum depression is one of the most common non-obstetric complications associated with childbearing, yet it remains underdiagnosed. Sensory symptoms—especially changes in the sense of smell—have received limited research attention.
This study assessed olfactory abilities in 39 mothers within the perinatal period who were screened with the Edinburgh Postnatal Depression Scale and compared them with case-matched healthy volunteers. Participants completed two testing sessions four weeks apart, including a standard odor detection threshold test and intensity and valence ratings for six odorants (three pleasant, three unpleasant).
Results showed no difference in odor detection thresholds between patients and controls, indicating intact early olfactory processing in PPD. However, the postpartum depressed group rated the three unpleasant odors as significantly less pleasant and perceived two odorants (one pleasant and one unpleasant) as less intense (p < 0.05). These effects did not significantly interact with the individual’s specific perinatal stage.
As the first study to evaluate olfactory function in postpartum depression, these findings suggest PPD may primarily affect higher-order olfactory perception—both hedonic evaluation and intensity judgment—rather than basic detection. These novel observations expand understanding of sensory symptoms in PPD and highlight the importance of further research into how pregnancy and the postpartum period alter sensory and affective processing.