16 Journal of Intellectual Disability - Diagnosis and Treatment, 2020, 8, 16-24 E-ISSN: 2292-2598/20 Comparison of Acceptance Commitment Therapy (ACT) and Cognitive Behavioral Therapy (CBT) in Reducing Depression symptoms and Increasing Happiness of Iranian adolescent Girl Students Forough Talaeizadeh * Department of Educational Science And Psychology, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran Abstract: This study aimed to compare the effectiveness of Acceptance and Commitment Therapy (ACT) and Cognitive- Behavioral Therapy (CBT) in reducing depression symptoms and increasing happiness of Iranian adolescent girls in Shiraz-Iran in 2017-2018 educational year. The research method was quasi- Experimental with assessing participants with pre -Test, Post-Test plans and control group. The Statistical population of this study consisted of 45 adolescent girl Students- between 13-17 years old - who were referred to the school’s student counselling centres because of their poor mental well being. They were selected by convenient sampling method and then they were randomly divided into three groups of 15 participants (two experimental groups and one control group). The Depression and Happiness variables were assessed by using Beck’s Depression Inventory (1996) and the Oxford Happiness Questionnaire (1989) respectively. Commitment Therapy Package was implemented for 8 sessions and Cognitive-Behavioral Package was implemented for 10 sessions for each Experimental groups separately. The Data were analysed by using SPSS24 software and analysis of multivariate covariance (MANCOVA). The results of this study suggested that both ACT and CBT Therapy approach had an acceptable effect on reducing Depression and increasing Happiness in Adolescent girls (p<0.05). However, the ACT had more influence on decreasing depression symptoms (1.56 %) and enhancing happiness (4.4. %) in participants outcomes in comparison with CBT method. Thus, it seems that ACT is a more effective intervention approach in this regard. Keywords: Acceptance-Commitment Therapy, Cognitive-Behavioral Therapy, Depression, Happiness, Adolescent Girls. INTRODUCTION The term “depression” describes a wide range of low emotions, including sadness to a state of pathological suicide. Depression is one of the most common mental disorders in the world [1]. The World Health Organization has reported that 21 million people around the world suffer from depression. It also predicts that unipolar major depression will be the leading cause of the disease by 2030 [2]. Various factors including biological, psychological and social factors are involved in the development of depression [3]. In the birth cycle of each individual, there is a critical period, which is placed between childhood and adulthood and is called adolescence. Adolescence is a phase of emotional instability, which is the transition from childhood to adulthood. Adolescence often involves isolation and stress. It involves guiding young people toward identity development and can be a difficult period [4]. Adolescents receive confusing *Address correspondence to this author at the Department of Educational Science And Psychology, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran; Tel: 0989173162794; Fax: 0987143311151; E-mail: ftalaeezadeh@yahoo.com messages, conflict with family and school, and face problems of self-knowledge and self-esteem. Depression is one of the most common and debilitating problems in youth and adolescents. It is widespread that it is referred to as psychological cold [5]. The first episode of this mood disorder usually occurs between the ages of 12 and 18 years [6]. According to a study conducted by Zargham in Isfahan- Iran, 78% of girls and 57% of boys had mild to very severe depression in the 13-17 years age group [5]. Depressed adolescents are too touchy feel that they are not useful and not attractive and have no value. During the depression, children and adolescents may show symptoms of anxiety such as fear of separation and physical symptoms such as stomach pain and headache. Mood irritability is seen and suicide is a real danger in these people [1]. Varieties of treatments, including acceptance and commitment therapy and cognitive-behavioural therapy have been used for the treatment of depressed adolescents. One of the effective treatments for reducing depression is acceptance and commitment therapy. Acceptance and commitment therapy has