Treatment resistant depression (TRD) is a disabling condition associated with a relevant psychosocial impairment worldwide.

This exploratory study is aimed to evaluate the main clinical and neurocognitive characteristics in a sample of 21 subjects admitted to the Psychiatric Clinic of University of Genoa as inpatients between 2015 and 2016 and diagnosed with TRD according to Thase and Rush staging method.

Patients have been assessed using the Hamilton Depression Rating Scale (HDRS), Hamilton Anxiety Rating Scale, and Clinical Global Impression (CGI). The Continuous Performance Test (CPT), Trial Making Test (TMT-A/B), Stroop Color Word Interference Test, Verbal Fluency Test, and Rey auditory-verbal learning test (RAVLT) have been administered as well.

Subjects with early-onset (< 50 years) depression had a longer illness duration, higher depressive episodes and more impaired performance at RAVLT while individuals with late-onset (> 50 years) depression showed a higher severity of depressive symptoms and more anxiety symptoms. Depressive symptoms were positively associated with anxiety (r = 0.82; P = 0.00) and negatively with TMT-A/B (r = −0.56, P = 0.01), Stroop Color Word Interference Test (r = −0.72, P = 0.005 and r = −0.616, P = 0.008), and RAVLT (r = −0.60; P = 0.02) performances. According to regression analyses, anxiety symptoms were the only significant predictor of depression severity (P = 0.02).

Early-onset depression is associated with more disability and worse neurocognitive performance whereas late-onset depression is linked to more anxiety symptoms and more depressive symptoms severity. Clinicians should closely monitor patients with TRD for the presence of anxiety symptoms that may represent a significant risk factor of poorer long-term outcome.

The authors have not supplied their declaration of competing interest.