Background. Rapidly changing industrial structures evidently increase individuals’ perceptions of not being in the preferred job, and also being ‘locked’ in the current post. The research on longitudinal associations of such locked-in situations with mental health is still scant, and there are controversial findings. The present study explored five hypotheses about mental health as a precedent and an outcome of different locked-in situations among permanently employed individuals. Methods. Survey data on depressive and functional somatic symptoms from age 16 to 43 and on locked-in situations (permanently employed in non-preferred job) at age 30 and age 43 were collected from 479 participants of the Northern Swedish Cohort Study. Based on these two measurements, the locked-in history was classified as ‘never’ (not locked-in at both ages), ‘early’ (locked-in at age 30 only), ‘late’ (locked-in at age 42 only) and ‘long’ (locked-in at both ages). Analysis of variance for repeated measures was used to compare the changes in mental health of the four subcohorts defined by the locked-in history.Results. Earlier evidence on the cross-sectional association between feeling locked-in and having poor mental health was confirmed. Longitudinal analyses revealed that those with poor baseline mental health at age 16 tend to get into a locked-in situation in the early middle age, that getting out of a locked-in situation in is associated with improving and getting into a locked-in situation is associated with worsening mental health, and that the worsening is more pronounced and the improvement less pronounced in white-collar than in blue-collar employees. Conclusions. Given that there are causal associations between locked-in situation and poor mental health, the findings clarify their bidirectional nature, as well as the importance of common methods bias and social class in studying these associations. With respect to labour policy, locked-in perceptions could be reduced by means of labour legislation, collective agreements and human resource management that enable smooth transitions between workplaces and occupations.

Background Rapidly changing industrial structures evidently increase individuals’ perceptions of not being in the preferred job, and also being ‘locked’ in the current post. The research on longitudinal associations of such locked-in situations with mental health is still scant, and there are controversial findings. The present study explored five hypotheses about mental health as a precedent and an outcome of different locked-in situations among permanently employed individuals. Methods Survey data on depressive and functional somatic symptoms from age 16 to 43 and on locked-in situations (permanently employed in non-preferred job) at age 30 and age 43 were collected from 479 participants of the Northern Swedish Cohort Study. Based on these two measurements, the locked-in history was classified as ‘never’ (not locked-in at both ages), ‘early’ (locked-in at age 30 only), ‘late’ (locked-in at age 42 only) and ‘long’ (locked-in at both ages). Analysis of variance for repeated measures was used to compare the changes in mental health of the four subcohorts defined by the locked-in history. Results Earlier evidence on the cross-sectional association between feeling locked-in and having poor mental health was confirmed. Longitudinal analyses revealed that those with poor baseline mental health at age 16 tend to get into a locked-in situation in the early middle age, that getting out of a locked-in situation in is associated with improving and getting into a locked-in situation is associated with worsening mental health, and that the worsening is more pronounced and the improvement less pronounced in white-collar than in blue-collar employees. Conclusions The findings clarify the bidirectional causal associations between locked-in situation and poor mental health, as well as the importance of common methods bias and social class in studying these associations. With respect to labour policy, locked-in perceptions could be reduced by means of labour legislation, collective agreements and human resource management that enable smooth transitions between workplaces and occupations. Key terms permanent employment; ANOVA for repeated measurements; occupational class