While knowledge on the neurobiological signatures of fear and anxiety disorders and, in particular, their association with treatment outcome is accumulating, clinical translation still awaits empirical proof of evidence. Exposure-based cognitive-behavioral therapy (CBT) is a first-line treatment, but clinically significant change is only seen in approx. 50-65% of patients. Patient stratification is a powerful option to increase treatment response; however, developing prognostic markers suitable for single-patient predictions still is in its infancy and crucially requires external cross-validation embedded within an a priori prediction approach - a procedure yet largely missing in the field of biomarker research. Employing a bicentric strategy the aim of this study is to test the hypothesis that a priori prediction of treatment outcome based on neurobiological measures is possible in a second, independent sample. Building upon findings from previous mechanistic studies, These will be incorporated into the development of a predictive pattern comprising fear-relevant genotypes and molecules targeting neuropeptides, related epigenetic signatures as well as neurofunctional activation patterns associated with fear circuitry functions, and clinical data. Pre-treatment neurobiological signatures will be tested for their potential as a predictive response marker towards behavioral exposure (virtual reality exposure treatment (VRET) and an in vivo behavioral avoidance test) in a model disorder of fear circuitry dysfunctions (spider phobia). Multivariate pattern analyses employing a machine learning framework will be used to generate predictions on the individual patient level and to cross-validate markers in a second, independent sample. While at site A predictions will be generated following completion of the treatment, response will be predicted at site B a priori, but in a double-blind manner. Comparison of observed vs. predicted response rates will serve as a test of hypothesis. In addition, neuroplastic (on a subsample) and epigenetic changes induced by VRET treatment will be assessed following treatment and, in case of epigenetics, also after 6-months follow-up.

Inclusion Criteria:

• 18 or older
• specific phobia (animal subtype: spider phobia) according to criteria of the Diagnostic and Statistical Manual of Mental Disorders, 5th Version (DSM-5)
• right-handedness
• Caucasian descent
• willingness to participate in massed exposure

Exclusion Criteria:

• patients exhibiting a primary other anxiety disorder (panic disorder, agoraphobia, social phobia, generalized anxiety disorder), acute suicidality, psychotic, bipolar I, obsessive-compulsive disorder, posttraumatic stress disorder, severe major depression, borderline personality disorder or substance dependency (except nicotine)
• patients fulfilling MRI-related exclusion criteria
• patients with current pharmacological or psychotherapeutic treatment, as well as those already previously treated with exposure-based CBT
• pregnancy or lactation