[Olfactory Dysfunctions: References to Neuropsychiatric Disorders and Diagnostics].

Past research has revealed a variety of olfactory deficits associated with psychiatric and neurodegenerative disorders. These deficits are evident in psychophysical olfactory testing as well as neurophysiological and neuroanatomical examinations. The specific type of olfactory dysfunction appears disorder specific. For example, with regard to affective disorders, the functional and anatomical overlap between olfactory and emotion-specific brain areas has been suggested as a major underlying factor for olfactory dysfunction. Based on converging evidence of changes in olfactory perception related to Major Depression, Schizophrenia, Alzheimer's and Parkinson's Disease, olfactory testing has been discussed as an important additional diagnostic marker. Hence, valid methods for objective and reliable olfactory testing as well as guidelines for the interpretation of the respective diagnostic findings are required. The aim of this review is to provide an overview of reported olfactory deficits in psychiatric and neurodegenerative disorders. In addition, a selection of olfactory tests, available in German-speaking countries, with regard to the respective disorder-related olfactory deficit in question are presented and classified. Original data regarding an empirical validation of the Düsseldorf Odour Discrimination Test in a clinical population are presented.