The Epidemiological Investigation For Subthreshold Depression In College Students And Efficacy Of Light Therapy For Subthreshold Depression

Objective: To evaluate the psychometric characteristics of the Center for Epidemiologic Studies Depression Scale(CES-D)in Guangzhou college students and to describe the prevalence of subthreshold depression among the college students(Study One).To examine efficacy of bright light therapy(BLT)and dim light therapy(DLT),compared with a waiting-list control(WLC)condition,for symptoms of depression and anxiety in college students with subthreshold depression(Study Two).Methods: Both studies recruited college students in Guangzhou,China.Study One: A total of 2068 college students were recruited by cluster random sampling method,and they were asked to respond to the CES-D,Beck Depression Inventory-II(BDI-II),and Positive and Negative Affect Schedule(PANAS).Construct validity,criterion validity and internal consistency of CES-D were examined.The Receiver Operating Characteristic(ROC)analyses were used to determine the optimal score for screening subthreshold depression.Depressive symptoms were compared by the CES-D score and factor scores of CES-D.Study Two: 144 college students who met the eligibility criteria for subthreshold depression were randomly assigned to one of the three conditions: BLT,DLT and WLC.The light intervention was administered by light boxes with light intensity settings of 5000 lux and 500 lux.The 8-week intervention consisted of daily exposure for 30 minutes in the morning(before 12 pm).No intervention was performed on participants in the WLC group.Assessments were conducted at baseline(week 0),during the trial(week 4),and after completion of the trial(week 8).The primary outcome was Hamilton Depression Rating Scale(HAMD)score,and secondary outcomes were BDI-II and State Anxiety Inventory(STAI-S)scores.Repeated measures analysis of variance was used to compare the original scores of the three groups,and univariate analysis of variance was used to compare the change scores of the three groups.Results: Study one: The final sample included 1,920 participants.Three factors(somatic symptoms,negative affect,and anhedonia)were extracted from CES-D by exploratory factor analysis.Confirmatory factor analysis results suggested that the newly derived model with 14 items was the best fit for our data.Cronbach’ s alpha of the 14-item CES-D was 0.87.The optimal cut-off point for screening for subthreshold depression was 16.CES-D score was not significantly differed at gender,grade,and major.Score of anhedonia in males was higher than that of females(P = 0.019)and the score of somatic symptoms in literature and management students was higher than those of medical students(P = 0.018).Study two: 144 participants were enrolled in the study but 2 participants dropped out from the trial during the intervention phase.Among the 142 participants who completed the trial,50 were allocated to the BLT group,50 to the DLT group,and 42 to the WLC group.From baseline to week 8,the HAMD score has significant interaction effect between time and group(F = 19.741,P < 0.001).The BLT(P <0.001)and DLT(P <0.001)were significantly superior to WLC,and the BLT was significantly superior to the DLT at week 8(P = 0.003).When comparing mean changes in HAMD score,BLT(P < 0.001)and DLT(P < 0.01)were significantly superior to the WLC,and the BLT was significantly superior to the DLT at week 8(P < 0.001).Mean changes in STAI-S scores of the BLT were significantly superior to WLC(P = 0.014).After the 8-week intervention,the response rates for the BLT,DLT and WLC groups were 70.0%,42.0% and 19.0%,respectively.Remission rates were achieved by 76.0%,54.0%,and 19.0%,respectively.Conclusions: The CES-D has good reliability and validity for assessing subthreshold depression in college students studying in Guangzhou.The prevalence of subthreshold depression among college students reached 31%.Male had greater anhedonia and literature and management students had greater somatic symptoms.Both bright light therapy and dim light therapy were efficacious in treating college students with subthreshold depression.Bright light therapy was superior to dim light therapy by the end of an 8-week trial.Bright light therapy was also efficacious in reducing anxiety.