38% of the PhD candidates at Leiden University are at risk of serious mental health problems. That is concluded by Inge van der Weijden and Ingeborg Meijer after having surveyed 250 PhD candidates and having interviewed twelve of them. Especially young and international candidates are at risk. Whether PhD candidates have an employment contract or not doesn’t affect their mental well-being, neither does autonomy or workload. However, how PhD candidates deal with their workload influences their mental health. This study used the same method as previous research at Flemish universities and found quite similar results. The full policy report is available in English and Dutch.