The Effects of Electroconvulsive Therapy or Repetitive Transcranial Magnetic Stimulation on Olfactory Sensitivity and Identification in Individuals with Depression
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Background: Previous research has found links between olfactory deficits and depression. Olfactory ability is restored with successful treatment with antidepressant medication. Electroconvulsive therapy (ECT) and repetitive transcranial magnetic stimulation (rTMS) are two effective treatments for depression. It is not known whether these somatic treatments may, similarly to pharmacotherapy, restore olfactory sensitivity and identification ability in individuals with depression. Objectives: The objective of the present study was to determine whether treatment with ECT or rTMS is associated with improvement in olfactory sensitivity or identification in individuals with depression. Methods: Six patients receiving ECT and three patients receiving rTMS completed the study. Before beginning treatment and 20-30 days after their first treatment, patients were assessed using the Smell Threshold Test (STT), Smell Identification Test (SIT), Hamilton Depression Rating Scale (HDRS), Beck Depression Inventory (BDI), and Snaith-Hamilton Pleasure Scale (SHPS). The control group consisted of nine matched healthy participants. Results: There was no significant difference between the ECT, rTMS, and control groups for olfactory sensitivity either before or after treatment. At both testing visits, the rTMS group performed significantly worse on olfactory identification compared to control, while the ECT group performed comparably to control. Olfactory identification ability was significantly correlated with HDRS score at baseline but not after treatment. Olfactory performance was not correlated with BDI or SHPS score. Conclusions: The results of this pilot study suggest that individuals with depression may not have decreased olfactory sensitivity ability compared to healthy controls. However, in those who do exhibit poor olfactory identification, rTMS may be effective in restoring sense of smell. Further research is needed to determine whether olfactory deficits are caused by depressive symptoms, and whether ECT may also restore olfaction in individuals who have olfactory deficits. Determining the links between olfaction and depression may be important for promoting the early diagnosis and treatment of depression, and for improving quality of life and everyday functioning.