Persistent Depressive Disorder Has Long-term Negative Impacts on Depression, Anxiety, and Somatic Symptoms at 10-year Follow-up Among Patients with Major Depressive Disorder

Objective: The study aimed to investigate the impacts of persistent depressive disorder (PDD) and pharmacotherapy on depression, anxiety, and somatic symptoms among patients with major depressive disorder (MDD) over a ten-year period.

Methods: 290 outpatients with MDD were enrolled, including 117 with PDD, at baseline. Subjects were followed-up at six-month, two-year, and 10-year points. MDD and dysthymic disorder were diagnosed using the Structured Clinical Interview for DSM-IV-TR. The Hamilton Depression Rating Scale, the Hospital Anxiety and Depression Scale, and the Depression and Somatic Symptoms Scale were used. Generalized Estimating Equation models were used to investigate the impacts.

Results: MDD patients with PDD had greater severities of depression, anxiety, and somatic symptoms at the three follow-up points as compared with those without; however, these results were of statistical significance only in patients without pharmacotherapy. MDD patients with PDD had a longer duration of pharmacotherapy and a lower remission rate as compared with those without. After controlling for depression and anxiety at baseline, PDD was independently associated with more severe depression, anxiety, and somatic symptoms.

Limitation: At the ten-year follow-up, approximately half of the subjects were lost to follow-up; this, in addition to the unequal follow-up intervals, might have caused bias.

Conclusions: Among the patients, PDD continued to have negative impacts on depression, anxiety, and somatic symptoms over the subsequent ten years. Differences in symptomatology between the patients with and without PDD were statistically insignificant when pharmacotherapy was utilized; however, pharmacotherapy did not fully compensate for the negative impacts of PDD.