Fig. 1

Study design of the multi-level assessment of patients with obsessive-compulsive disorder (OCD) before and after psychotherapy. The psychological level comprises the OCD symptom severity (Y-BOCS), depression symptom severity (BDI-II) and overall symptom severity (SCL-90). The neural level consists of the regions of the cortico-striato-thalamic-cortical network (CSTC). On the neurochemical level, the concentrations of the neurotransmitters dopamine and serotonin, inflammatory parameters (IL-6, IL-10, and TNF-α), cortisol, and the brain-derived neurotrophic factor (BDNF) were assessed. For all variables, the pre-post difference (Δ) was calculated and evaluated