The study will evaluate two group CBT interventions delivered by school health nurses, in cooperation with community psychologist and mental health care personnel, to adolescents with mild to moderate levels of anxiety symptoms. The two interventions have different intensity (5 versus 10 group meetings). The two group interventions will be compared to a waitlist control group.

Anxiety disorders are among the major mental health problems in children and adolescents, with regard to prevalence and long-term consequences. Cognitive behavioural therapy (CBT) has proven to be effective as treatment, early intervention and prevention of youth anxiety disorders. The majority of youth with anxiety problems, however, is not in contact with mental health services and do not receive effective help. This is due to shortage of personnel, resources and time among mental health-personal delivering treatment, as well as health services not being easily accessable for adolescents. School-based, low-intensity early intervention programs (indicated prevention) may improve access to effective treatment for youth with internalizing problems, and also promote more effective use of health services. The present study is a multi-site randomized controlled study with early intervention to be conducted within the primary health care service in three parts of Norway; including nine municipalities from west, east and south of Norway. A brief CBT program will be compared to a longer CBT program, and a wait-list control group. The effects will be evaluated with regard to decrease in youth internalizing symptoms. The CBT interventions are given to adolescents with mild to moderate levels of anxiety symptoms. Interventions are delivered by trained school-health nurses in collaboration with and/or supervised by experienced CBT therapists. The study involves researchers from three research environments in Norway, and collaboration with prominent international researchers from USA and Australia.The study has potential impact on how to deliver effective low-threshold interventions to anxious youth.

Inclusion Criteria:

1. An overall score of > 25 on the anxiety inventory Spence Children's Anxiety Scale (SCAS) and a score of > 1 on the first question of the Children's Anxiety Life Interference Scale (CALIS), indicating that anxiety interferes with daily life of the youth, rated either by the adolescents or by one parent.
2. The adolescent and at least one parent understand and read Norwegian.
3. Assent from the youth and signed informed consent from the parent.

Exclusion Criteria:

The adolescent has a behavior that makes participation in groups with other adolescents challenging. This is evaluated by the school nurse, based on information from the adolescent, the parent and the teacher. In each case, the school nurse makes an evaluation based on the following questions:

1. Is the adolescent able to follow group-rules?
2. Will the adolescent behave in ways that disrupts the group?
3. Does the adolescent have learning problems to an extent that will make it difficult to follow the group program?