"How much of the cave hasn’t been discovered yet?" It’s actually one of the top questions asked at Carlsbad Caverns National Park–and one that not one ranger can answer.
How common is sibling sexual trauma? How many people’s lives have been forever changed by it? How many children don’t tell anyone? How many people don’t even remember what they went through themselves?
We know sibling sexual trauma happens. A lot. But the numbers that we do have need to be qualified. They are estimates, based on limited and incomplete information. Where do they come from?
The entry room of the cave represents official crime data: the cases that get reported to police, and recorded by police. These can give a raw number of reports of criminal sexual activity against a sibling that were investigated, charged or convicted. But sexual violation by a child within the family is the type of sexual offense least likely to be reported to police. Many cases that are reported are not seriously investigated, because the legally admissible evidence to prove a crime of this type is so difficult to obtain. The likelihood that harmful sexual activity will be reported or recorded as abuse is also influenced by unconscious bias on the part of both mandatory reporters and investigators. Even when they do file a report, police do not always record the relationship between the victim and the offender. A recent report in the UK has advocated for reporting sibling sexual abuse as a separate category so that it can be seen and measured.
More of the cave comes into view when adults are surveyed anonymously, asking about their childhood experiences. Most researchers survey a “convenience sample,” a relatively small group of people who are easily accessible. Frequently-cited samples have included students taking a psychology class, inpatients in a psychiatric setting, even girls in an internet chat room. The data from these should not be assumed to apply universally.
A few studies have sampled an entire population as best they can–for example, by randomly telephoning thousands of households over a large area. Population-wide surveys of adults give us our best estimates of how much of the cave is hidden. The surveys consistently include significant numbers of respondents who say they were sexually abused as a child but have never told anyone about it before. In the largest study to report specifically about siblings, only 12% of college students who identified any kind of sexual experience with a sibling had ever told anyone else about it.
It is important to note that studies asking adults about their childhood experiences may not reflect today’s rates or risk factors for being harmed by a sibling’s abusive sexual behavior. Even a well-designed survey of young adults can only reflect what was happening in the society and technology 10 to 20 years past. It is also important to note that surveys must be very carefully worded and conducted if they are to truly include sibling-caused sexual trauma. The UK’s Sibling Sexual Abuse Project 2020-2022 found that many survivors of sibling sexual abuse do not identify as having experienced child sexual abuse. And few surveys will reach the people whose lives have been most devastated by their trauma–those who are incarcerated, or homeless, or too physically ill or mentally distraught to participate.
The deepest, unexplored part of the cave represents the victims of sibling sexual trauma who do not have any memory of the abuse to report. Intrafamilial sexual abuse, including sibling sexual abuse, is especially shocking and traumatic, which makes it particularly prone to becoming at least temporarily inaccessible to conscious memory (dissociative amnesia). Some of these survivors find their memories triggered later in life–a jarring experience to say the least. Currently it is conservatively estimated that at least 10% of children who are sexually abused will experience a time of not remembering the abuse, followed by delayed recall.
Based on the information we have now–the small portion of the cave that has been explored–5WAVES estimates that at least 3-5% of all children are affected by sibling sexual trauma. But the true extent of the problem and number of children affected remains a deep secret, one no one can answer, but one that cries out for more exploration, more research.