Background Suicide is a leading cause of death among adolescents and emerging adults. Suicidality is a multidimensional construct that includes suicidal ideation (SI), self-harm (SH), suicide attempts, and suicide completion, without a fixed or linear progression between these elements. We examined the course of suicidality (SI/SH) over adolescence and young adulthood (age 11–29) and correlates of natural remission and recovery over these 18 years, using the Dutch population-based longitudinal TRAcking Individuals Lives Survey (TRAILS). We examined whether perceived belongingness and social support are associated with recovery from suicidality, for example, as predicted by the Interpersonal Theory of Suicide.Methods TRAILS followed 2229 adolescents aged 11 (SD = 0.6, 49% women) and we studied to age 29, with 7 waves 2–3 years apart. The prevalence of suicidality and changes therein were quantified using the Adolescent/Youth Self-report (Achenbach system), and we examined potential psychosocial and demographic correlates, such as self-esteem, self-efficacy, temperament/personality, and cognitive style, socioeconomic status, and gender.Results The correlation between SI/SH increased from early adolescence (age 11 r = ~ .33) to stabilize over mid adolescence (ages 15–29, r = ~ .50). SI was somewhat more common in youth (4.4–8.3%) than SH was (1.9%-5.3%) and peaked earlier in time (SI, age 11) than SH (age 14), and suicidality declined gradually over adolescence and young adulthood. The low base-rate of SI/SH in our prospective general population sample proved a significant barrier to investigate the specific mechanisms of natural recovery in suicidality, as luckily > 90% of youth reported no suicidality.Conclusion Protective and recovery factors for SI and SH remain difficult to identify, and apparently require general population studies of twenty thousand adolescents or more in the Western world. Complementary risk samples and time series or process approaches, interviews, and psychological autopsy studies can help identify prevention and protective factors to reduce suicidality among youth.