A comparison of the familiality of chronic depression in recurrent early-onset depression pedigrees using different definitions of chronicity.
BACKGROUND
The study of chronicity in the course of major depression has been complicated by varying definitions of this illness feature. Because familial clustering is one component of diagnostic validity we compared family clustering of chronicity as defined in the DSM-IV to that of chronicity determined by an assessment of lifetime course of depressive illness.


METHODS
In 1750 affected subjects from 652 families recruited for a genetic study of recurrent, early-onset depression, we applied several definitions of chronicity. Odds ratios were determined for the likelihood of chronicity in a proband predicting chronicity in an affected relative.


RESULTS
There was greater family clustering of chronicity as determined by assessment of lifetime course (OR=2.54) than by DSM-IV defined chronic major depressive episode (MDE) (OR=1.93) or dysthymic disorder (OR=1.76). In families with probands who had preadolescent onset of MDD, familiality was increased by all definitions, with a much larger increase observed for chronicity by lifetime course (ORs were 6.14 for lifetime chronicity, 2.43 for chronic MDE, and 3.42 for comorbid dysthymic disorder). Agreement between these definitions of chronicity was only fair.


CONCLUSIONS
The data used to determine chronicity were collected retrospectively and not blindly to relatives' status, and assessment of lifetime course was based on global clinical impressions gathered during a semi-structured diagnostic interview. Also, it can be difficult to determine whether individuals with recurrent major depressive episodes who frequently experience long periods of low grade depressive symptoms meet the strict timing requirements of DSM-IV dysthymic disorder.


CONCLUSIONS
An assessment of lifetime symptom course identifies a more familial, and thus possibly a more valid, type of chronic depression than the current DSM-IV categories which are defined in terms of particular cross-sectional features of illness.
Mondimore
Francis M
FM
Department of Psychiatry and Behavioral Sciences, School of Medicine, Johns Hopkins University, Baltimore, MD 21287, USA. fmondimo@jhmi.edu
Zandi
Peter P
PP
MacKinnon
Dean F
DF
McInnis
Melvin G
MG
Miller
Erin B
EB
Schweizer
Barbara
B
Crowe
Raymond P
RP
Scheftner
William A
WA
Weissman
Myrna M
MM
Levinson
Douglas F
DF
DePaulo
J Raymond
JR
Potash
James B
JB
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D002908:Chronic Disease; D003710:Demography; D003865:Major Depressive Disorder / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D016584:Panic Disorder / Q000453:epidemiology / Q000523:psychology; D010375:Pedigree; D012008:Recurrence; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013406:Suicide, Attempted / Q000706:statistics & numerical data