Did Neve Lafferty and Georgia Rowe jump to their deaths off the Erskine Bridge because they were mistakenly placed in a ground-floor flat with easy exits, and because there weren't enough staff on duty that evening at the Good Shepherd Open Unit in Bishopton?

Or did such headlines only explain why they were able to kill themselves on that day in October 2009, as Sheriff Ruth Anderson herself admitted this week in her Fatal Accident Inquiry (FAI) report?

Did they actually die through the impact of whatever happened in their past: their deaths at 14 and 15 a tragedy waiting to happen, rehearsed in a cumulative, disturbing list of numerous suicide attempts, abscondings and self-destructive chaos, painstakingly described in the full report?

That's a vital question if future tragedies are to be reduced, given that many young people in the care system have similar behaviour. Those headline findings may be almost painfully unimportant.

Of course, Sheriff Anderson had to include immediate circumstances, but an FAI can also encompass background issues, since the purposes of such discretionary inquiries include finding the cause or causes: "The defects ... in any system of working which contributed," and, "Any other facts ... relevant to the circumstances of the death."

Sheriff Anderson rightly highlighted some background features to this distressing case – including inconsistency and lack of communication among care agencies during the girls' lives. Her report regretted the absence of comprehensive risk assessments for every young person in care, which covered absconding, self-harm and suicide, and "a more robust approach to the issue of absconding".

Thorough risk assessments are indeed necessary but are merely the beginning of a process. The key questions are why any given young person is a high suicide risk and what work is needed to reduce their sense that life is unbearable?

One element noticeably missing from a caring, conscientious report is a look behind a frequent cause of suicide and self-harm: the consideration, even naming, of severe childhood trauma and its damaging effects.

Incidentally, there is a wider issue here about how concerned people may give specialist input to an FAI: Sheriff Anderson advised me it would be inappropriate even to consider a brief submission I sent urging background trauma to be discussed in her report, as I was not a witness to the inquiry, and evidence must be introduced by the Crown or "an interested and represented party".

Since in most types of inquiry submissions are welcomed, this was unexpected, raising the obvious, circular question of how anyone seeking to contribute constructively can become a witness or interested party if they are neither known about nor called in the first place. It seems important the Crown clarifies this, so that in future anyone in Scotland with serious concerns about vulnerable victims knows how these might be heard at an FAI.

It might surprise some that the importance of childhood trauma is often not acknowledged in residential care. I have spoken to sincere workers, even those in secure care, who have told me that they didn't raise the subject of abuse with young people in their care because the answer might mean they had to launch an investigation.

Yet the report's catalogue of Neve and Georgia's distressing symptoms over years would be recognised in the child protection field as absolutely classic "serious-end" behaviour usually seen among children who have suffered abuse. There is also the high possibility that the girls suffered sexual exploitation (they kept absconding from care and being found in strange men's flats or cars, having been plied with drink and drugs).

From the age of seven Georgia showed sexualised behaviour and strange dissociative episodes reminiscent of trying to fight off assault. She reacted violently to restraint. She took huge amounts of numbing alcohol and drugs as did Neve, while both spoke frequently about wanting to die, making serious and graphic attempts.

Children with this history need two things most: consistent safety and skilled therapy by specialists.

In cases such as this, absconding is not trivial – as long ago as the mid-1980s it was being suggested this needed to be taken more seriously, with clear policies on reducing and investigating absconding, a crucial source of sexual and physical danger to vulnerable young people. Why is it still lacking? If children abscond and are exploited in the process, each time such degradation happens it is likely to further undermine their self-esteem.

Dotted through this full report, good professionals strongly recommended or tried to provide therapy, but little ever took place. If, like Neve and Georgia, young people often reject it, you have to persist in trying – as do some excellent Scottish voluntary sector organisations I have worked with.

Fears, taboos and excuses about lack of training persist throughout residential settings about working with, or even acknowledging, past trauma, and about keeping young people truly safe – including from each other at times.

This is fiddling while Rome burns, like seeing as relevant whether these desperate girls lived on the ground floor or the first floor.

That's why I wanted this report to include serious discussion about how any earlier life-risks or dangers Neve and Georgia faced had been dealt with by care services, about measures to protect them from others, not just from themselves, and, crucially, about whether any skilled trauma work took place at the Good Shepherd, other care centres or in earlier placements.

Sadly, awkward silences about such awkward subjects will, it seems, continue.

One of the recommendations to the FAI by Stephen Platt, Professor of health policy research at the University of Edinburgh, stated in the full report, was that: "Professionals working with looked-after and accommodated children, either directly (eg in residential establishments) or indirectly (eg local general practitioners or employed in the local Child and Adolescent Mental Health Services team) should have a sound understanding of the risk of self-harm and suicide among their clients and of appropriate interventions to mitigate that risk. Appropriate training should be provided on starting employment in a residential centre and at regular intervals thereafter."

However, these "appropriate interventions" urgently need to include skilled trauma work by an individual staff member or a regularly visiting specialist with the young people, most of whom will have experienced trauma.

If social work supervision, residential care and mental health teams cannot routinely address with young people the very issues most likely to have caused their chaotic behaviour and self-denigration, control measures will merely postpone many early deaths, or ensure – to be blunt – that these happen on someone else's watch, not theirs. Or on the streets, through violence or an overdose.

Dr Sarah Nelson is a researcher specialising in childhood abuse and its effects, based at Edinburgh University.