Prevalence and factors associated with fatigue in patients with major depressive disorder or bipolar disorder

Aims: To study the prevalence of fatigue and factors associated with fatigue in patients with major depressive disorder (MDD) or bipolar disorder (BD). Methods: Two hundred fifty-three outpatients with MDD or BD at the initial assessment were used to study the prevalence of fatigue and relationship between fatigue and other clinical correlates. The severity of fatigue was measured with Iowa Fatigue Scale (IFS), and depression and anxiety symptom-severity were measured with the QIDS-16-SR (the 16-item Quick Inventory of Depressive Symptomatology - Self-Report) and Zung-SAS (Zung Self-Rating Anxiety Scale). Correlation between IFS and QIDS-16-SR total scores, QIDS-16-SR item scores or Zung-SAS total scores, and independent factors associated with fatigue was assessed with simple or multiple linear regression analysis. Results: Overall, 28.4 % of MDD and 29.8 % of BD patients did not have fatigue, but 41.2 % of MDD and 45.0 % of BD patients had fatigue, and 30.4 % of MDD and 25.2 % of BD patients had severe fatigue. Depression/anxiety severity was significantly correlated with fatigue. However, after controlling current psychiatric comorbidities, demographics, some social factors, and psychotropic use, only QIDS-16-SR scores were still significantly and positively correlated with IFS scores in both MDD and BD. Differential correlations between IFS scores and item scores of QIDS-16-SR in MDD and BD were observed. Limitation: Cross-sectional. Conclusions: In this outpatient sample, fatigue was highly prevalent in patients with MDD or BD. The independent association of depressive severity with the severity of fatigue highlights the importance of complete resolution of depressive symptoms in treating MDD and BD.