Carrera M, Herrán A, Ramírez ML, Ayestarán A, Sierra-Biddle D, Hoyuela F, Rodríguez-Cabo B, Vázquez-Barquero JL. Personality traits in early phases of panic disorder: implications on the presence of agoraphobia, clinical severity and short-term outcome. Objective: To explore the relations between personality traits using the Big Five model and presence of agoraphobia, clinical severity and short-term outcome in an unbiased clinical sample of never-treated panic disorder patients. Method: Panic disorder (PD) patients (n = 103) in the first stages of their illness were evaluated using the Neuroticism-Extraversion-Openness Five Factor Inventory of Personality (NEO-FFI) and were compared with a sample of healthy subjects. Severity was assessed by the Panic Disorder Severity Scale and the Clinical Global Impression Scales. Patients were evaluated after 8 weeks of naturalistic pharmacologic treatment with Selective Serotonin Reuptake Inhibitors. Results: Panic disorder patients show more neuroticism than healthy subjects. Patients suffering from agoraphobia are more introverted than controls. Extraversion, in addition to gender and distress, during panic attacks allows to correctly classifying 72% of the cases of agoraphobia. Conclusion: Low scores in extraversion contribute to explain the presence of agoraphobia in panic disorder. Personality traits are neither related to clinical severity nor to short-term response to pharmacological treatment.