While I was researching on the net about children labour and looking at pictures, I noticed that a lot of children not only looked much older than their age, with haunted faces. On a lot of pictures I noticed the 1000 yard stare like soldiers with PTSD have. Is this a result of the photographic technics and possibilities of that time or had these kids really PTSD?
This is not a direct answer to your question but to signpost to an interesting individual case for which we have documents.
Robert Blincoe was a pauper child in London who was sent to be an apprentice at Litton mill in Derbyshire in the early 1800s. His account of his time there including starvation, torture and abuse was published in 1828 and was a key source for those who sought to improve both conditions in factories and treatment of the very poor.
It is impossible not to read Blincoes account and the distress the memories give him without wondering whether we would now consider this as ptsd.
This is a link to a pdf of the memoirs produced by a local history group in Derbyshire, although the memoir is elsewhere on the web and was recently republished. The memoir starts at page 35, but there is much of interest in the early parts of the document.