Euthymia: It Depends on How You Define It

In clinical trials, euthymia in bipolar disorder is conventionally defined as scores below a certain threshold, but not zero, on the Young Mania Rating Scale (YMRS) and Hamilton Rating Scale for Depression (HRSD). The persistence of mild symptoms might have influenced the findings from a recent study, in which researchers examined learning in response to reward in 13 “euthymic” patients with bipolar disorder and 25 healthy controls. Patients’ mean YMRS and HRSD scores were 1.9 and 3.4, respectively; their scores on a scale measuring anhedonic depression were significantly higher than those of controls.

Participants completed a computer task in which two possible answers were presented with equal frequency; one answer was intermittently rewar…