This paper examines whether the simultaneous occurrence of two or more adverse life course transitions has a stronger effect on mental health compared to the effects of the sum of each. The focus is on four life course transitions (partner loss (divorce/separation or death), death of a parent, unemployment, disability) and the data come from a large four-wave longitudinal dataset in the Netherlands (N = 4,192 respondents). There is clear evidence that negative life course transitions tend to cluster. Of the four transitions, partner loss and disability onset have the largest negative impact on mental health but unemployment also has a clear effect. There is not only additive but also interactive accumulation during the life course: one adverse event has a more negative impact on mental health when it occurs simultaneously with another. This provides evidence on the link between ‘turbulent times’ in the life course and negative mental health trajectories. We did not find evidence that effects of adverse transitions depend on education.