The purpose of this study is to develope web-based cognitive behavioral therapy for Korean adoldescents who have a mild depression. And we will investigate whether web-based cognitive behavioral therapy is more effective than supportive psychotherapy for treating depressed adolescents. Our hypothesis is web- based cognitive behavioral is more effective than supportive psychotherapy

We will recruit adolescents(age 12-18 years old) with a diagnosis of major depressive disorder, dysthymia and depressive disorder NOS in outpatient clinic of child and adolescent psychiatry and we will advertise for recruitment of subjects in community. The study protocol will be approved by the Institutional Review Board of the Hallym university sacred heart hospital. Well- trained interviewers will conduct the assessments of participants and their parents or guardians. The assessment included the diagnostic interview, demographic characteristics, depressive symptom severity scale , Columbia suicide severity rating scale, questionnaire about abuse histories.

We decided the number of participants of 164, because in previous studies, web- based cognitive behavioral therapy showed mild to moderate effect size (effect size = 0.43). So for examining the hypothesis, we will recruit 164 adolescents by calculating the number of participants using G power program version 3.1.3. (level of significance = 5%, power of a hypothesis test = 80%, drop out rate = 20%)

And we will conduct randomized controlled trial for examining the efficacy of web- based cognitive behavioral therapy. Our hypothesis is web- based cognitive behavioral is more effective than supportive psychotherapy, so we will deliver web- based cognitive behavioral therapy program to cognitive behavioral therapy group for 8 weeks(once in a week), and supportive psychotherapy to supportive psychotherapy group for 8 weeks(once in a week) We will exclude the participant if the participant has severe depressive symptoms, definite suicidal idea, plan and attempt, psychotic symptoms, bipolar disorders, sexual abuse histories, other neurological diseases or received cognitive behavioral therapy, pharmacotherapy or interpersonal psychotherapy.

We will analyze the intent- to- treat population. For each individual, missing values are replaced by the last observed value of that variable. And we will use Chi square test or repeated measure-ANOVA.

Inclusion Criteria:

• Clinical diagnosis of major depressive disorder, dysthymic disorder and depressive disorder NOS
• participants and their parents both agree informed consents

Exclusion Criteria:

• participants have psychotic symptoms, developmental disorders,
• participants are diagnosed by bipolar disorder
• participants are current high risk of suicide
• participants have psychiatric and physical symptoms need urgent medicine treatment
• participants have a history of sexual abuse
• participants have cognitive behavioral therapy or interpersonal psychotherapy within 3 months
• participants have a history of brain injury or a neurological disorder such as seizure disorder, or severe physical disorder