Prevalence, incidence and stability of anxiety among adolescents in the general population

Abstract

The background for the present thesis is the lack of empirical knowledge concerning the prevalence and natural trajectories of various and common types of anxieties among adolescents. At the start of this thesis, no large scale epidemiological studies existed in Scandinavia, and internationally the same was true for prospective studies on changes in anxiety during adolescence in the general population.

The aims of the thesis were: (1) to estimate characteristics of the distribution of anxiety among adolescents in a large Norwegian community sample of 13-18-year old adolescents (paper I), (2) to examine the one-year stability and changes in anxiety for girls and boys during early adolescence (13-15 years) (paper II), and (3) to explore the factor structure and factor invariance of the Norwegian version of the SCARED (paper III).

The thesis was designed both as a cross-sectional study examining a representative sample of 1802 adolescents aged 13-18 years in mid-Norway, and as a 1-year prospective study of 946 13-15 year olds enrolled in junior high school. The main instrument for measuring anxiety was the widely used and standardized Screen for Child Anxiety Related Emotional Disorder (SCARED) which was translated into Norwegian. Its 5- factor structure was replicated also in the present Norwegian sample of adolescents, and we also found evidence for sex and age invariance of the factor structure.

Our main findings replicated findings from earlier international research on two central points: Girls reported significantly higher anxiety symptom levels than boys, and for both sexes, total mean anxiety levels, when measured with the SCARED were stable, or showed only a small decline during adolescence.

However, our results also implicated gender-specific trajectories for normal anxiety in that 14-year-old girls, unlike boys, reported a transient large increase in anxiety levels which returned to lower levels within a year. In addition, our results implicated a large individual variability/instability in the magnitude of anxiety symptom levels during the one year follow-up for early adolescents of both sexes. Consequently, large natural “remissions” from high levels of anxiety (47.5% of high-scorers) and equally large incidence rates were found (8.2% of total sample).

There is a great need for more empirical knowledge regarding anxiety in children and adolescents. More research is needed on the diagnostic criteria for different age groups, and more importantly, on the prognosis for high symptom levels in children and adolescents to provide better guidelines and foundation for choosing appropriate treatment for this age groups but also for the planning of mental health services