Toward a definition of a cyclothymic behavioral endophenotype: which traits tap the familial diathesis for bipolar II disorder?
BACKGROUND
Although the cyclothymic temperament appears to be related to the familial diathesis of bipolar disorder, exhibiting high sensitivity for bipolar II (BP-II) disorder, it is presently uncertain which of its constituent traits are specific for this disorder.


METHODS
In a sample of 446 major depressive patients (BP-II and unipolar), in the French National EPIDEP study, the cyclothymic temperament was assessed by using clinician- and self-rated scales. We computed the frequency of individual traits and relative risk for family history of bipolarity.


RESULTS
From both clinician- and self-rated scales, four items related to mood reactivity, energy, psychomotor and mental activity were significantly highly represented in the subgroup with positive family history of bipolarity. The item "rapid shifts in mood and energy" obtained the highest relative risk (OR=3.42) for positive family history of bipolarity.


CONCLUSIONS
These findings delineate those cyclothymic traits which are most likely to tap a familial-genetic diathesis for BP-II, thereby identifying traits which can best serve as a behavioral endophenotype for this bipolar subtype. Such an endophenotype might underlie the cyclic course of bipolar disorder first described in France 150 years ago by Falret and Baillarger.
Hantouche
E G
EG
Université Paris VI Mood Center, Hôpital Pitiè-Salpêtrière, Paris, France.
Akiskal
H S
HS
D001714:Bipolar Disorder / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics; D003527:Cyclothymic Disorder / Q000145:classification / Q000453:epidemiology / Q000235:genetics; D003865:Major Depressive Disorder / Q000453:epidemiology*; D003937:Diagnosis, Differential; D039721:Diagnostic and Statistical Manual of Mental Disorders; D004198:Disease Susceptibility; D006801:Humans; D008403:Mass Screening / Q000379:methods; D010641:Phenotype; D015995:Prevalence; D011581:Psychological Tests; D011596:Psychomotor Disorders / Q000175:diagnosis / Q000453:epidemiology; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013694:Temperament