The study will only detect hypomanic symptoms in treatment resistant MDD patients by mean of HCL-32 administration. Further re-evaluation of MDD diagnosis is not a direct aim of the study. No efficacy and tolerability of pharmacological treatments will be assessed. Patients matching inclusion and exclusion criteria will be enrolled consecutively; each investigator will include the first 10 to 40 patients that will be visited as treatment resistant MDD.

Inclusion Criteria:

• Written informed consent form
• Male and Female age: 18-65 years
• Diagnosis of MDD according to DSM-IV TR (296.3 x Major Depressive Disorder, recurrent)
• Treatment resistance defined as non-response to at least 2 antidepressants given in an ade

Exclusion Criteria:

• Patients already participating in clinical trial or any other interventional study
• Patients unable to understand HCL-32 item meaning

Patients with treatment resistant major depressive disorder will be evaluated in order to assess the presence of hypomanic symptoms as cause of resistance.