Luby, Joan et al. Journal of the American Academy of Child & Adolescent Psychiatry.  Published online October 2018

This study of 288 children aged 6-11 years referred for a psychotherapy treatment study of depression found rates of non-suicidal self-injury in 21.3%, self-harm in 19.1% and suicidal behaviour in 3.5% in this clinical population.  Children with SI/SB or NSSI experienced a greater frequency of violent life events than children with no SI/SB/NSSI. Children with SI/SB had significantly more preoccupation with death compared to subjects with NSSI and subjects with no SI/SB/NSSI. Children with SI/SB had more vegetative signs of depression and greater depression severity and those with NSSI were more irritable with higher depression severity than those with no SI/SB/NSSI.  These findings indicate that suicidal thoughts and behaviours occur in children and that they should be explored during clinical assessment of this age group.

https://www.jaacap.org/article/S0890-8567(18)31886-0/fulltext