Recent studies indicate that Adult Separation Anxiety Disorder (ASAD) may represent a discrete diagnostic entity worthy of attention. Adults with ASAD report estreme anxiety and fear about separations from major attachment figures. These symptoms 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) in patients with panic disorder with associated 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 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) 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, 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.

Reduction of platelet TSPO density in our sample of patients with depression was specifically related to the presence of ASAD. These data suggest that TSPO expression evaluation is a useful biological marker of ASAD.