There was a significant association between level of education and psychological distress in both genders, those with low education reporting most symptoms of distress. This association was especially strong in women in the age group 55–67 years.
Sense of mastery accounted for about half of the association between level of education and psychological distress, whereas the other variables contributed less to explain the association.
It is a strength of the study that it is based on a an extensive nation wide sample, matching well the population with respect to age, gender and place of living in Norway, and with register based data on socio-demographic variables (education, income and marital status). The response rate, 70%, is somewhat low, and this may to some extent have influenced the results. Even if there may be some under-representation of people with mental and social problems, which is likely to be the case in such studies, this should not to any substantial degree invalidate the internal comparison of groups, which is the focus of the present study.
As a measure of income, one may question the use of net income, as it is known that many of real high income earners have a low net income. This might reduce the association between household income and psychological distress in the study, but it is difficult to say how it would effect the association between sense of mastery and psychological distress. Anyhow, it is not likely that this will substantially influence the main results of the study.
In the context of the present study, it is a weakness that we are dealing with cross-sectional data, which makes it difficult to draw conclusions about causality.
The finding that the association between level of education and psychological distress is strongest in women above the age of 55 years, is somewhat surprising. A possible explanation could be that women in this age group, when their eventual children are grown up, and their role in the family context is less central, will have problems when entering the labour marked if they are lacking in education. In men the problems with lacking education is likely to be stronger in the younger age groups, when problems on the labour market is difficult to combine with the establishment of a family.
The finding that sense of mastery emerged as an important mediating factor between education and psychological distress is in accordance with other studies suggesting that lack of control plays an important role in explaining the association between social inequality and mental health [21
]. It leaves open, however, two questions: Why is level of education associated with sense of mastery, and why is sense of mastery associated with psychological distress?
One possibility is that the association between sense of mastery and level of education is explained by psychological selection: Because of lower coping skills, which might be explained by genetic and/or early environmental factors, those with low sense of mastery are less likely to succeed in the school system, and end up with little formal education [21
Another possibility is that low sense of mastery is a reflection of the life situation of people with low education and low social status. Without education the possibility to control one's life situation is reduced, not least with respect to options on the labour marked. Hence environmental factors may influence the sense of mastery [24
]. Obviously, factors of psychological selection and factors of environment may play together, and re-enforce each other in positive or negative feed-back circles. The present study, however, does not allow for drawing conclusions about the causation of sense of mastery.
Why is sense of mastery associated with psychological distress? One possibility is that low sense of mastery in itself is a stressor [21
]. Another possibility is that low sense of mastery is associated with other stressors, like unemployment, low income, weak social support and negative life events, and hence has an indirect effect on mental health. The last possibility, however, seems unlikely in the present study, as the association between sense of mastery and psychological distress was only slightly reduced when adjusting for the other variables. So the study seems to support the hypothesis that low sense of mastery is a stressor in itself.
Because of the strong association between sense of mastery and psychological distress, the possibility of overlapping concepts has been raised. The principal component analysis, suggesting that we are dealing with two separate factors, weakens this hypothesis. Also a scatter-plot points in the direction of two different factors.