The number of children (pre-teens) using illegal drugs is small in most countries but still worrying.
Neil McKeganey of Glasgow University’s centre for drug misuse research (Scotland) said he was shocked to find that just under a third of children under 13 in Glasgow and Newcastle had been exposed to illegal drugs and 3.9% had tried them, 1.5% in the previous month. After interviewing 2,318 children aged 10-12 in the two cities, he estimated there were 60 pre-teen heroin users in Glasgow and 34 in Newcastle.
Though not seen widely in ‘developed’ countries, drug and alcohol abuse among street children in ‘third’ or ‘second world’ countries is quite a common occurrence, such as in Jakarta, Indonesia.

Pregnant mothers who use addictive substances is also another factor in this topic, especially the current opioid crisis that is increasing around the world. See links below.