['Platelets (PLT), which serve as the primary hemostatic indicator, can be used as a peripheral model for studying monoamine turnover in the brain. Therefore, they are attractive targets as circulatory biomarkers for the detection of psychiatric disorders. However, PLT counts have not been utilized as a peripheral biomarker of psychopathology.', "This study was a retrospective analysis of PLT counts upon admission of 108drug-naïve adolescents hospitalized in an inpatient psychiatric department. PLT counts of patients with suicidal ideation (SI) were compared with those of nonsuicidal in patients (NSI) and those of 77 healthy adolescents, serving as a control group. The patients' disorders were diagnosed and classified by one of four American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders, 4th ed. (DSM IV) diagnoses, that is, unipolar depression, bipolar depression, schizophrenia, and a pooled group of conduct and borderline personality disorders.", 'Significantly higher PLT counts were observed in SI patients, as compared with NSI patients (300,200±53.3/mL vs. 253,900±53.2/mL, respectively; p=0.0001). A significant difference in PLT counts in SI patients, relative to the control group, was also noted (300,200±53.3/mL vs. 254,000±52/mL, respectively; p=<10(-26)). Finally, a significant difference in PLT counts was observed between conduct/borderline personality disorders patient with and without suicidal ideation (292,000±55/mL vs. 246,000±64/mL, respectively; p=0.001).'] Are suicidal thoughts associated with platelet counts in adolescent inpatients?