Introduction
Psychological distress is widespread among young people and seems to be socially patterned. However, socioeconomic differences in psychological distress among children and adolescents may be less pronounced in welfare states with low economic disparity, e.g. the Nordic countries. The available studies are inconclusive and difficult to compare because of differences in study populations and measurements.
Therefore the objective of this paper is to use standardised data from 5 Nordic countries to analyse socioeconomic variations in psychological distress among young people.

Methods
We used data from the international Health Behaviour in School-aged Children (HBSC) study 2005/2006 in five Nordic countries: Denmark, Finland, Iceland, Norway and Sweden. In each country, the study population was 11-, 13- and 15-years old students in a random sample of schools or school-classes, n=28,299. The outcome measure was psychological distress measured as experiencing at least one psychological symptom (irritability or bad temper, feeling low, or feeling nervous) daily. Two different indicators of socioeconomic position were used: 1) Family Affluence Scale (FAS) which measures material conditions in the family (high, medium, low) and 2) parents’ occupational social class (OSC) measured by father’s and mother’s occupation (highest ranking parent: high, medium, low, unclassifiable). We performed age-adjusted multilevel logistic regression analyses stratified by sex and country.

Results
The overall country level prevalence of experiencing at least one psychological symptom daily ranged from 8.1 % (Denmark) to 13.2% (Iceland). All countries displayed a socioeconomic gradient.

FAS: Odds for experiencing at least one psychological symptom daily increased by decreasing FAS. The Odds Ratio (OR) for psychological distress was 1.36 (95% CI 1.25-1.48) in the medium FAS-group and 2.07 (95% CI 1.78-2.40) in the low FAS-group. The association appeared in all countries although only significant in Iceland and Sweden (girls only).

OSC: The Odds Ratio (OR) for psychological distress was 1.01 (95% CI 0.89-1.15) in the medium OSC-group, 1.37 (1.24-1.52) in the low OSC-group and 1.66 (95% CI 1.49-1.85) in the unclassifiable OSC-group. For girls this finding was robust and significant across all countries except Sweden. For boys the association was graded but not significant.

Implications
A socioeconomic gradient of psychological distress exists among young people in the Nordic welfare countries. This observation calls for the development of mental health promotion especially effective among young people with low socioeconomic position.