Olfactory bulb volume predicts therapeutic outcome in major depression disorder.

The volume of the olfactory bulb (OB) is strongly reduced in patients with major depressive disorder (MDD) and this group exhibits markedly decreased olfactory function. It has been suggested that olfactory input is important for maintaining balance in limbic neurocircuits. The aim of our study was to investigate whether reduced OB volume is associated with response to therapy in MDD. Twenty-four inpatients (all women, age 21-49 years, mean 38 ± 10 years SD) with MDD and 36 healthy controls (all women, age 20-52 years, mean 36 ± 10 years SD) underwent structural MRI. OB volume was compared between responders (N = 13) and non-responders (N = 11) to psychotherapy. Retest of OB volume was performed about 6 months after the end of therapy in nine of the patients. Therapy responders exhibited no significant difference in OB volume compared to healthy controls. However, average OB volume of non-responders was 23 % smaller compared to responders (p = .0011). Furthermore, OB volume was correlated with the change of depression severity (r = .46, p = .024). Volume of the OB did not change in the course of therapy. OB volume may be a biological vulnerability factor for the occurrence and/or maintenance of depression, at least in women.

Olfaction as a marker for depression in humans.

BACKGROUND: Animal studies show a strong link between the loss of olfactory function and depressive behavior. We analyzed, whether olfactory function is a marker for depression in humans. If so, reduced olfactory function can be expected in depression that improves to level of normality after successful antidepressive treatment. METHODS: Twenty-seven female in-patients with depression were compared to 28 healthy age-matched women at the beginning and at the end of antidepressive therapy or at two visits, respectively. Olfactory function was assessed comprehensively including threshold, discrimination and identification testing, chemosensory event related potentials and olfactory functional magnetic resonance imaging. RESULTS: At the beginning of psychotherapy the patients exhibited reduced olfactory discrimination, prolonged latencies of the event-related potential and reduced activation in secondary olfactory structures (thalamus, insula, and left middle orbitofrontal). After therapy, patients improved significantly in all of the parameters and consequently the differences between control group and patients vanished. LIMITATIONS AND CONCLUSION: We conclude that olfaction is a marker for depression. However, the results are limited to a relatively selective sample of depressed women.

Reduced olfactory bulb volume in adults with a history of childhood maltreatment.

The human olfactory bulb (OB) is the first relay station of the olfactory pathway and may have the potential for postnatal neurogenesis in early childhood. In animals, chronic stress affects the OB and olfactory functioning. For humans, it has been shown that major depressive disorder is accompanied by reduced OB volume and reduced olfactory function. However, it is not clear if major stress in childhood development also affects olfactory functioning and OB volume in humans. OB volume was measured and olfactory function was tested in 17 depressive patients with and 10 without a history of severe childhood maltreatment (CM). CM patients exhibited a significantly reduced olfactory threshold and identification ability. The OB volume of the CM patients was significantly reduced to 80% of the non-CM patients. In conclusion, postnatal neurogenesis might be by reduced in CM, which may affect olfactory function of the brain in later life. Alternatively, a reduced OB volume may enhance psychological vulnerability in the presence of adverse childhood conditions although other areas not analyzed in this study may also be involved.