Functional and Metabolic Changes in the Course of Antidepressive Treatment

The study will investigate functional and metabolic changes in the course of antidepressive treatments. The investigators will apply different imaging methods to investigate the effects of antidepressive interventions on resting state neural activity, functional activiation during cognitive and emotional stimulation, neurotransmitter concentrations as well as concentrations of brain- derived neurotrophic factor. The investigators hypothesize that antidepressive interventions modulate the excitatory glutamatergic system and thereby increase either the concentration of glutamate or the glutamate/ glutamine ratio. These metabolic changes are accompanied by altered functional activation in medial and lateral prefrontal areas during emotional and cognitive stimulation, respectively. After longterm treatment, excitatory glutamate and inhibitory gamma-aminobutyric acid concentrations adapt to a new homeostatic level which is reflected in antidepressive response or remission of symptoms. The investigators assume that the levels of glutamate and gamma-aminobutyric acid determine the amplitude of BOLD responses during emotional and cognitive stimulation. Furthermore, the investigators hypothesize that the plasma concentration of brain- derived neurotrophic factor might be a predictor for therapy response and changes in the course of treatment. With our protocol we adhere to the rules of good scientific practice and observe all relevant laws, regulations and guidelines that pertain to the project. The investigators' study is in compliance with the Declaration of Helsinki and approved by the local ethics committee. Storage of data is in accordance with german privacy laws.