Major depressive disorder (MDD) is a disorder defined by mood disturbance, but the deficits in emotional reactivity that accompany MDD are not yet fully characterized. Researchers have utilized the emotion-modulated startle paradigm to investigate emotional responding among depressed individuals with mixed results. Inconsistent results may be due in part to the heterogeneity of mood disorders, including variation in mood severity. The current study utilized an emotion-modulated startle procedure with 33 individuals currently experiencing a major depressive episode, 25 individuals currently experiencing a minor depressive episode (mD), and 31 healthy controls. Severity of depression, anxiety, and positive and negative mood states were ascertained on the sample. Emotion-modulated startle failed to differentiate between mood disordered individuals and healthy controls. However, results found a significant association between abnormal patterns of emotion responding and positive affect (PA), such that individuals with low PA showed exaggerated responding to unpleasant stimuli. The results suggest that PA may be an important dimension in mood disorders that underlies abnormal emotional responses.

Major depressive disorder (MDD) is a debilitating disorder characterized by significant mood disturbance. In laboratory studies, MDD has been characterized by both blunted positive (PER) and negative emotional reactivity (NER). However, mood disordered persons' emotional reactivity has rarely been studied in naturalistic settings, and it is unknown how less severe forms of depression relate to emotional reactivity. To address these issues, the current study utilized two naturalistic sampling methods (the Day Reconstruction Method and the Experience Sampling Method) to examine PER and NER to daily life events in 35 individuals currently experiencing a major depressive episode (MDD), 26 individuals currently experiencing a minor depressive episode (mD), and 38 healthy controls. Both methods demonstrated that individuals with major and minor depression exhibited blunted PER relative to controls. In surprising contrast to previous laboratory findings, both individuals with MDD and mD showed increased NER relative to controls. Correlational analyses with severity measures indicated that depression and anxiety severity were positively related to NER and negatively related to PER. Findings suggest that NER in mood disorders may diverge as a function of assessment context and may be heightened in naturalistic environments. Despite the fact that mD is a milder mood disorder, findings suggest that mD results in similar emotional impairments as found in MDD.