This article analyses secular trends in suicide and parasuicide and provides support for the hypothesis that a true increase in these phenomena has occurred since the early 1950s up to at least the early or mid-1980s among the adolescent and young adult populations of Europe and North America, particularly young men. One of the potential causal mechanisms for this development, increasing secular trends in and lowering of age of onset for depressive disorders, is examined. Although it is difficult to assess whether the earlier age of onset observed for depressive disorders is reflected in an increase of suicide mortality at a lower age, there is indirect evidence to suggest that this might be the case. Studies show that lifetime parasuicide prevalence rates for the general population do not exceed and sometimes even remain below the rates for adolescents. Assuming that recall of past episodes remains constant throughout the life span, one possible explanation for this finding is an earlier age of the first-ever parasuicidal act. Since parasuicide is an important precursor of suicide, a lowering of age for first-ever parasuicides can be expected to lower the age for suicides and increase the overall lifetime risk.