Abstract
ObjectivesThe Delta Study was undertaken to improve the diagnosis of mood disorders in individuals presenting with low mood. The current study aimed to estimate the prevalence and explore the characteristics of mood disorders in participants of the Delta Study, and discuss their implications for clinical practice.MethodsIndividuals with low mood (Patients Health Questionnaire‐9 score ≥5) and either no previous mood disorder diagnosis (baseline low mood group, n = 429), a recent (≤5 years) clinical diagnosis of MDD (baseline MDD group, n = 441) or a previous clinical diagnosis of BD (established BD group, n = 54), were recruited online. Self‐reported demographic and clinical data were collected through an extensive online mental health questionnaire and mood disorder diagnoses were determined with the World Health Organization Composite International Diagnostic Interview (CIDI).ResultsThe prevalence of BD and MDD in the baseline low mood group was 24% and 36%, respectively. The prevalence of BD among individuals with a recent diagnosis of MDD was 31%. Participants with BD in both baseline low mood and baseline MDD groups were characterized by a younger age at onset of the first low mood episode, more severe depressive symptoms and lower wellbeing, relative to the MDD or low mood groups. Approximately half the individuals with BD diagnosed as MDD (49%) had experienced (hypo)manic symptoms prior to being diagnosed with MDD.ConclusionsThe current results confirm high under‐ and misdiagnosis rates of mood disorders in individuals presenting with low mood, potentially leading to worsening of symptoms and decreased well‐being, and indicate the need for improved mental health triage in primary care.
Highlights
Regarding participants who had been previously diagnosed with Major depressive disorder (MDD), the findings from the current study revealed that 31% met the criteria for bipolar disorder (BD) according to the Composite International Diagnostic Interview (CIDI)
While we found no significant differences in depression severity between BD and MDD in those with no previous mood disorder diagnosis, participants with by intermittent depressive and manic (BDI) previously diagnosed as MDD scored higher on the Patient Health Questionnaire-9 (PHQ-9) relative to MDD and low mood individuals, potentially reflecting the effects of receiving ineffective treatment and the lack of support due to incorrect diagnosis
Given that depressive episodes in BD and MDD patients with no previous mood disorder diagnosis were largely indistinguishable, standard screening practices must go beyond brief symptom-count checklists, such as the PHQ-9 (Kroenke et al, 2001), when assessing the symptoms of those presenting with depressive symptoms
Summary
The secondary objective of the Delta Study was to identify patients with MDD among undiagnosed low mood individuals To this end, three patient groups were recruited. To achieve study recruitment targets, 5,422 symptomatic individuals were enrolled, of which 3,232 completed the online mental health questionnaire and 924 completed the CIDI diagnostic interview. No other significant group differences were observed in participants with no previous mood disorder diagnosis Of those who had been previously diagnosed with MDD, participants with newly diagnosed BDI were more likely to smoke relative to the MDD and subthreshold BD groups. Individuals with BDI had lower levels of education in comparison to those with MDD, and rated their mental health as being worse relative to the low mood group. The average time interval (±standard deviation) between the diagnosis of MDD and the diagnosis of BD was 5.4 ± 5.9 years, and the average duration of BD diagnosis was 7.3 ± 6.6 years
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