BMC Public Health 2008, 8:159 http://www.biomedcentral.com/1471-2458/8/159 Risk of unemployment was measured with the question "How big is the risk that you can involuntarily become unemployed?" The question had four answer alternatives (1 = high, 4 = no risk) and was dichotomised as yes if the answer was high or some risk (= 1) and no if low or no risk (= 0) (possible mediator). The question "People look down on me" had a 7-grade scale from disagree to completely agree [35]. The scale was dichotomised at the 75th percentile. The proportion above the cut-off point was defined as those who felt that others look down on them (= 1) (possible mediator). Many other possible confounders, such as education and indicators of externalising problems (such as alcohol con- sumption and use of narcotics) could have been included in the analyses. However, due to the risk of multicolline- arity the number of possible confounders had to be kept low. For example, the education variable was excluded from the model due to its high correlation with social class among women (0.480). Results Table 1a and 1b show the distribution of the dependent and independent variables among men and women sepa- rately in different labour market positions, i.e. among those who were without permanent employment, had obtained permanent employment and had permanent employment. Among women, but not men, significant differences in the psychological symptoms at age 30 were found between those without permanent employment com- pared to those who had obtained a permanent job as well as those with permanent employment. Overall, those men (and to a lesser extent women) without permanent employment were worse off than those with permanent employment and those who had obtained a permanent job. With one exception (risk of unemployment) the situa- tion of those who had obtained a permanent job did not differ significantly from those who had permanent employment. Gender differences were tested within the three groups of labour market position between Tables 1a and 1b, and only found for social class among those without perma- nent employment, where more men than women were of low social class (p = 0.031). Among those in permanent employment, women had more often children (p = 0.024) and financial problems (p = <0.001) as well as poorer psychological health at both age 16 and 30 (p = 0.005) compared to men. Women who became perma- nently employed had poorer psychological health at both ages 16 and 30 than men (p = <0.001). A separate analysis of labour market activities among those without permanent employment at age 25, i.e., dur- ing the first year of the exposure period for the variable "unstable labour market position", showed that 32 per- cent were unemployed, 15 percent had occasional jobs, 14 percent were in labour market programmes while the rest were in studies or in permanent employment (data not shown in the tables). As regards the excluded group, the majority had permanent jobs (62 percent), while 25 percent were studying. The correlations between labour market position, psycho- logical symptoms at age 16 as well as all confounders and mediators included in the model (p = <0.05) are shown in Additional file 1. The highest correlations were found between labour market position and risk of unemploy- ment among both men (0.362) and women (0.344). A multivariate logistic regression was performed in order to analyse whether the transition from an unstable labour market position to permanent employment was associ- ated with psychological symptoms. The results are pre- sented in Table 2. The multivariate analysis showed that the odds ratio for the psychological symptoms was significantly lower in the groups obtaining permanent employment and with per- manent employment, compared to the group without per- manent employment. Also, psychological symptoms at age 16, not having the chance to do what one would pre- fer to do, high demands and "people look down on me" had strong associations with psychological symptoms at age 30. A separate bivariate analysis was performed to analyse the association between psychological symptoms at age 30 and the variable labour market positions (data not shown in the tables). For those who obtained permanent employment the odds ratio for psychological symptoms was 0.26 (95% CI 0.16–0.43) and for those in permanent employment the odds ratio was 0.19 (95% CI 0.09–0.41). Compared with the results in Table 2, there were no major changes of the OR for permanent employment, while the OR for obtaining permanent employment diminished. Two other indicators of health-related selection were also tested – psychological health (measured with questions identical to those used at age 16 and at age 30 and dichot- omised in the same way) at age 18 and at age 21. If health- related selection was measured at 18 respectively at age 21 the OR for having lower scores of psychological symp- toms at age 30 among those who obtained permanent employment was 0.34 (95% CI 0.18–0.63) respectively 0.39 (95% CI 0.21–0.74). Also, if the health-related selec- tion was measured at 18 respectively at age 21 the OR for Page 7 of 11 (page number not for citation purposes)