Positive Affective Dynamics In Individuals With Subthreshold Depression

BackgroundThe phenomenon of positive affect(PA)reduction,a core feature of major depressive disorder(MDD),has driven various studies identifying the multiple abnormal indices of positive affective dynamics in people with MDD.Positive psychology also affirmed the important role of PA in combating depression.In fact,PA is not only related to the improvement of life satisfaction,but the recovery of PA may in turn contribute to the reduction of negative affect(NA),thereby improving the emotional function and social behavior.Subthreshold depression(StD),existing on a spectrum with MDD,is often regarded as the precursor of MDD.However,StD still remains unnoticed because it falls short of the diagnostic criteria for MDD.To this end,we examined the positive affective dynamics in individuals with StD integrating laboratory-based and ecological approaches to help understand the emotional characteristics of StD and to provide research basis for the early identification of depressive disorders.Participants and methodsLaboratory study:The two-stage method was adopted to screen college students and divide them into StD group and healthy controls(HC)group.In the laboratory setting,31 StD and 39 HC individuals experienced laboratory positive mood induction by using an eight-minute comedy clip,which was used to assess positive emotional intensity and duration of emotional response.The least square curve fitting method was used to evaluate the PA intensity,positive emotional reactivity and emotional duration.Ecological momentary assessment(EMA):In order to generalize laboratory findings to real world and further explore other indices of positive affective dynamics,53 StD and 64 HC in ecological momentary assessment reported their emotional states 14 times a day for a week.Multilevel models were performed to test the effects of group predicting PA intensity and PA inertia.ResultsResults showed that in the laboratory context,PA intensity was significantly lower in the StD group than that in HC group at each measured timepoint(ps<0.001).StD could get the same intensity of subjective positive emotional experience as HC(t=0.20,p=0.84),whereas results of curve fitting revealed that the StD group had difficulty maintaining it.Moreover,compared with HC group,StD cases’ positive emotional experience decreased significantly.in the first 3 minutes after emotion elicitation(t=2.50,p=0.02).Consistent with one of the laboratory findings,EMA also found that StD individuals had significantly lower PA intensity at each hour of the day than HC(ps<0.001).In addition,results of EMA further explained reduced capacity to sustain PA,manifested in significantly greater PA inertia in StD than HC in multilevel models(b=0.05,SE=0.02,p=0.013).ConclusionsIndividuals with StD were characterized by lower PA and shorter emotional duration.Their high PA inertia in daily life reflected resistance to mood change,which may further explain anhedonia and difficulty in emotional maintenance.Altogether,these findings give insight into aberrant positive affective dynamics in StD cases and highlight the need for early identification of StD.