SSRI-reduced platelet reactivity in non-responding patients with life-long Recurrent Depressive Disorder: Detection and involved mechanisms.

•RDD SSRI patients show blunted aggregatory responses towards collagen and epinephrine.•Their platelets are relatively more resistant to mechanical stress, characterized by higher morphology scores.•RDD SSRI patients show inherent absence of platelet micro-aggregates on DIC microscopy.•The mechanisms involved in the observed abnormalities include peripheral serotonin disbalance and abnormal α-AR function.•Microscopic evaluation might be useful for detection of the reduced PLT function.