Persistent Depression as a Novel Diagnostic Category: Results from the Menderes Depression Study

Persistent depressive disorder (PDD) introduced in the Diagnostic and Statistical Manual of Mental Disorders (DSM) 5 as a novel diagnostic category represents a consolidation of two separate DSM-IV categories, chronic major depressive disorder (MDD) and dysthymic disorder. The present study aims to investigate the frequency and clinical as well as socio-demographic correlates of PDD in comparison with those of episodic MDD among patients seeking treatment for depressive symptoms.

Participants were 140 depressive out-and in-patients under treatment at the psychiatry clinic of the Adnan Menderes University Research Hospital. Each patient was assessed by means of a structured clinical interview (SCID-I) and relevant psychometric instruments including the Hamilton Depression Inventory and Eskin Suicidal Behavior Inventory.

Among the depressive patients, 61% fulfilled the criteria for PDD and 39% for episodic MDD. As compared with patients with episodic MDD, the PDD patients were older (d=.54), lower in educational attainment (d=.55), more likely to have comorbid generalized anxiety disorder (OR=3.7), and more prone to report symptoms of anxiety, hopelessness, pessimism, and somatic complaints. Nevertheless, the PDD patients displayed heterogeneous characteristics with respect to clinical severity and suicidal behavior.

Our findings suggest that majority of depressive patients, including those fulfilling the criteria for MDD, have been suffering from a persistent ailment rather than an episodic disorder. Clinicians with a cross-sectional perspective are more likely to diagnose MDD, whereas those with a longitudinal perspective are more likely to identify PDD in the majority of depressive patients. The incorporation of both of these perspectives into DSM-5 in a complementary manner will possibly enhance our insight into depressive disorders and improve our treatment results.