["Recent studies indicate that Adult Separation Anxiety Disorder (ASAD) may represent a discrete diagnostic entity worthy of attention. Adults with separation anxiety report extreme anxiety and fear about separations from major attachment figures (partner, children or parents). These symptoms affect individual's behavior, lead to severe impairment in social relationships and are not better accounted for by the presence of agoraphobia. In a previous study we found platelet expression reduction of the 18 kDa Translocator Protein (TSPO) (the new nomenclature for the peripheral-type benzodiazepine receptor) in patients with panic disorder who also fulfilled the diagnostic criteria for ASAD.", 'To explore whether separation anxiety might be a factor differentiating TSPO expression in a sample of patients with major depression.', 'The equilibrium binding parameters of the specific TSPO ligand [3H]PK 11195 were estimated on platelet membranes from 40 adult outpatients with DSM-IV diagnosis of MDD, with or without separation anxiety symptoms, and 20 healthy controls. Patients were assessed by SCID-I, HAM-D, the Structured Clinical Interview for Separation Anxiety Symptoms (SCI-SAS-A) and the Adult Separation Anxiety Self-report Checklist (ASA-27).', 'A significant reduction of platelet TSPO density mean value was found in depressed patients with associated ASAD symptoms, while no significant differences were found between depressed patients without ASAD and the control group. Individual TSPO density values were significantly and negatively correlated with both SCI-SAS-A and ASA-27 total scores, but not with HAM-D total score or HAM-D anxiety/somatization factor score.'] Is platelet 18 kDa Translocator Protein density reduced in depressed patients with adult separation anxiety?