Depression severity and quality of life of qualified and unqualified patients with a mood disorder for a research study targeting anhedonia in a clinical sample.

OBJECTIVE: To investigate the depression severity and quality of life of qualified and unqualified patients with a mood disorder for a research study based on anhedonia severity.

METHODS: Diagnosis of major depressive disorder (MDD) or bipolar disorder (BPD) was ascertained with the MINI International Neuropsychiatric Interview. The severity of depression was measured with the 16-item Quick Inventory of Depressive Symptomatology-Self-Report (QIDS-16-SR), and Item 5, "feeling sad (sadness)," QIDS-16-SR Item 13, "change in general interest," was used to measure the severity of anhedonia. The quality of life was measured with the Quality of Life, Enjoyment and Satisfaction Questionnaire (Q-LES-Q).

RESULTS: Of 96 patients with MDD and 147 with bipolar I or II disorder, the severity rating on sadness and anhedonia was similar. The severities of anhedonia and sadness were highly correlated with R2 of ≥0.91. Without considering depressive severity, 55% of patients would be eligible for a study if≥mild anhedonia was used as a severity criterion, but only 26% of patients eligible for a study if≥moderate anhedonia was used without considering substance use and medical comorbidities. If patients with ≥ moderate overall depressive symptoms were considered, 88.1% of patients would be eligible if≥mild anhedonia was required for a study, and 45.2% of patients would be eligible for a study if≥moderate anhedonia was required. For those who were unqualified for the study based on≥moderate anhedonia, about 1/3 had≥moderate overall depressive symptoms and less than 40% of maximum possible scores of Q-LES-Q. If only patients in remission based on overall depressive symptom severity were considered for a study of anhedonia, no patient would be eligible for the study.

CONCLUSION: Depressive mood and anhedonia are highly correlated. Screening patients with a mood disorder and an overall moderate depressive severity is a cost-effective approach for a study targeting anhedonia, especially for a study requiring≥moderate severity of anhedonia. However, 1/3 of the unqualified patients will have≥moderate overall depressive symptoms and poor quality of life.