This systematic review and meta-analysis found that the pooled prevalence of suicidal ideation among children 12 and under was 7.5% (28 studies), the pooled prevalence of suicide attempts was 1.3% (6 studies) and that the pooled prevalence of non-suicidal self-injury was 21.9% (2 studies).

Prevalence of Suicidal Ideation and Behaviors in Children Aged 12 Years and Under: A Systematic Review and Meta-Analysis DO – 10.2139/ssrn.4011899

https://www.thelancet.com/journals/lanpsy/article/PIIS2215-0366(22)00193-6/fulltext#seccestitle10