Evolution of "Other Specified Depressive Disorder" Across DSM and ICD Versions
Critical Clarification on Terminology
The term "other specified depressive disorder" is a DSM-5 construct that does not have direct equivalents in earlier DSM versions or in ICD systems, which used different nomenclature and conceptual frameworks for subthreshold or atypical depressive presentations.
DSM Evolution (DSM-III through DSM-5-TR)
DSM-III and DSM-IV Era
- Earlier DSM versions (DSM-III and DSM-IV) classified depressive presentations that didn't meet full criteria under broader "Not Otherwise Specified" (NOS) categories rather than "Other Specified" designations 1
- The DSM-IV maintained "Mood Disorders" as a unified chapter encompassing both bipolar and depressive disorders, with depressive disorder NOS serving as the catch-all category 2, 3
DSM-5 Fundamental Restructuring
- DSM-5 eliminated the unified "Mood Disorders" chapter and separated it into distinct "Bipolar and Related Disorders" and "Depressive Disorders" chapters, reflecting evidence that major depressive disorder is genetically and neurobiologically distinct from bipolar disorder 2, 3
- The "Not Otherwise Specified" terminology was replaced with two new categories: "Other Specified Depressive Disorder" (when the clinician chooses to specify the reason criteria are not met) and "Unspecified Depressive Disorder" (when the clinician chooses not to specify) 1, 3
- DSM-5 introduced dimensional assessment through transdiagnostic specifiers including "with mixed features," "with psychotic features," and "with anxious distress" to characterize symptom presentations more precisely 4
DSM-5 Diagnostic Threshold Changes
- The diagnostic threshold for major depressive disorder may have been effectively lowered through two key changes: addition of "hopelessness" as a symptom descriptor and removal of the bereavement exclusion 4
- These changes potentially reduced the number of cases falling into "other specified" categories by expanding what qualifies as major depressive disorder 4
DSM-5-TR Continuity
- DSM-5-TR maintains the same fundamental categorical structure as DSM-5, with both systems remaining primarily categorical despite incorporating dimensional elements 5
ICD Evolution (ICD-10 through ICD-11)
ICD-10 Approach
- ICD-10 maintained a purely categorical approach without dimensional expansions for depressive disorders 5, 6
- ICD-10 used "dysthymia" as a separate diagnostic entity requiring at least four out of ten symptoms with two being core symptoms (depressed mood, loss of interest, or increased fatigability) 6
- ICD-10 did not have a direct equivalent to DSM's "other specified depressive disorder" but used different threshold criteria that created distinct boundaries 7
ICD-11 Major Changes
- ICD-11 fundamentally restructured the entire mental disorders chapter, introducing dimensional symptom specifiers across six domains: positive symptoms, negative symptoms, depressive symptoms, manic symptoms, psychomotor symptoms, and cognitive symptoms 5, 8
- ICD-11 raised the diagnostic threshold for depressive episodes to match DSM-5, requiring at least five out of ten symptoms (compared to four out of ten in ICD-10), with one symptom being depressed mood or diminished interest or pleasure 7
- The additional tenth symptom in ICD-11 is "hopelessness," which research demonstrates outperforms more than half of DSM symptoms in differentiating depressed from non-depressed individuals 7
ICD-11 Dimensional Qualifiers
- ICD-11 added dimensional qualifiers for depressive episodes including melancholic features, anxiety symptoms, panic attacks, and seasonal pattern, allowing more detailed clinical characterization beyond categorical diagnosis 5, 6
- The system allows rating symptom severity across domains on a 4-point scale ranging from "not present" to "present and severe," providing flexibility for treatment planning without requiring precise temporal calculations 5
ICD-11 Bereavement Distinction
- ICD-11 maintained a raised diagnostic threshold during bereavement (requiring symptom persistence for at least one month and presence of at least one symptom unlikely in normal grief), diverging from DSM-5's elimination of bereavement exclusion 7
- This approach is supported by research showing that bereavement-related depression has significantly lower risk for recurrence compared to non-bereavement-related depression 7
ICD-11 Dysthymia Decision
- The ICD-11 Committee determined that evidence was insufficient to combine dysthymic disorder and chronic major depressive disorder into a single category (as DSM-5 did with "persistent depressive disorder"), maintaining dysthymia as a separate diagnostic entity 6, 7
- Instead, ICD-11 uses a qualifier "current episode persistent" when diagnostic requirements for depressive episode have been met continuously for at least two years 7
Clinical Performance Data
ICD-11 Field Studies
- Field studies with 928 clinicians showed 82.5% to 83.9% rating ICD-11 as quite or extremely easy to use, accurate, clear, and understandable compared to ICD-10 5, 6
- Interrater reliability was high for psychotic disorders but only moderate for mood disorders, with reliability for dysthymic disorder noted as "improvable" despite overall improvements 5, 6
- Diagnostic accuracy advantages were largely limited to entirely new diagnostic categories rather than improvements in existing ones 5
Key Divergences Between Current Systems
Mixed States Classification
- ICD-11 maintains "mixed episode" as a separate category (consistent with ICD-10), while DSM-5 eliminated this category in favor of a "with mixed features" specifier applicable to manic, hypomanic, and depressive episodes 7