Subjective Olfactory Dysfunction Shows Stronger Link to Depression Than Objective Impairment: JAMA
Sweden: Researchers have found in a new systematic review and meta-analysis that subjective olfactory impairment is consistently associated with depression. In contrast, objective olfactory impairment is linked to depression primarily in older adults and individuals with anosmia, suggesting that subjective and objective smell deficits may reflect partly distinct underlying mechanisms.
The findings, published in JAMA Otolaryngology–Head & Neck Surgery by Henry Bode of the Karolinska Institute, Stockholm, Sweden, and colleagues, highlight the relationship between olfactory dysfunction and depression in the general population. The researchers noted that both conditions are common in older adults and are linked to poorer quality of life, cognitive decline, and increased mortality, suggesting that olfactory impairment may serve as a potential marker of late-life depression.
To evaluate the evidence, the investigators conducted a systematic review and meta-analysis of population-based cross-sectional and longitudinal studies examining the association between olfactory impairment and depression. Literature searches were performed across PubMed, Embase, EBSCOhost, and Web of Science through July 11, 2024, without language restrictions.
The analysis included 23 studies representing 17 independent cohorts involving 187,056 participants. The mean age of participants was 63.6 years, and 63% were women. After excluding overlapping cohorts, the primary analyses included seven independent studies evaluating subjective olfactory impairment and 11 studies assessing objective olfactory impairment.
Key findings from the study include:
- Subjective olfactory impairment was associated with a 56% higher odds of depression.
- The association between subjective smell impairment and depression remained significant in studies with a low risk of bias.
- The relationship was consistent across different age groups.
- Similar associations were observed regardless of whether depression was assessed using subjective or objective measures.
- Objective olfactory impairment showed a modest association with objectively measured depression in the primary analysis.
- However, this association weakened after adjustment for potential publication bias.
- Despite this, objective olfactory impairment remained significantly associated with depression among adults aged 65 years or older.
- A significant association was also observed in individuals with anosmia, indicating that severe smell loss may be particularly relevant to depression risk.
The authors suggested that subjective smell impairment may reflect an individual's perception of olfactory decline and its emotional impact. In contrast, objective olfactory impairment is associated with depression mainly in older adults and people with anosmia, indicating partly distinct underlying mechanisms.
They concluded that longitudinal and mechanistic studies are needed to clarify whether olfactory impairment contributes to depression or serves as an early marker. The researchers also urged clinicians to be aware of the observed association, while noting that its clinical significance remains to be established.
Reference:
Bode H, Sjöberg L, Ekström I. Olfactory Impairment and Depression: A Systematic Review and Meta-Analysis. JAMA Otolaryngol Head Neck Surg. Published online July 09, 2026. doi:10.1001/jamaoto.2026.1758
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