Having autism can sometimes mean enduring a litany of traumatic events, starting from a young age. And for many, those events may add up to severe and persistent post-traumatic stress disorder (PTSD).

Before Gabriel could even talk, his father’s girlfriend at the time told him his mother had abandoned him. At age 3, he was sexually abused by a cousin. He was mercilessly bullied once he started school, showed signs of depression by age 7 and by 11 began telling his mother he did not want to live. About three years ago, while at summer camp, he almost drowned. Shortly after that, he experienced life-threatening heatstroke when he went to get his Legos from the car trunk and accidentally locked himself in. Six months ago, just after his grandmother died, he attempted suicide.

“He’s been hurt and had so much disruption in his life that he’s having problems realizing that he has stability now,” says his mother, Kristina. (Kristina and Gabriel’s last names have been withheld to protect the family’s privacy.) “The world is chaotic and crazy for typically developed people. For him, it’s overwhelming and confusing.” Gabriel, now 13, started seeing a therapist about five years ago and last year was diagnosed with PTSD.

Gabriel’s autism was a contributing factor in most of the harrowing incidents he went through. Clinicians suspect that the condition increases the risk for certain kinds of trauma, such as bullying and other forms of abuse. Yet few studies have investigated that possibility or the psychological aftermath of such trauma, including PTSD.

“We know that about 70 percent of kids with autism will have a comorbid psychiatric disorder,” says Connor Kerns, assistant professor of psychology at the University of British Columbia in Vancouver, Canada. Depression, anxiety and obsessive-compulsive disorder are all known to be more common among autistic people than in the general population, but PTSD had largely been overlooked. Until a few years ago, only a few studies had delved into the problem, and most suggested that less than 3 percent of autistic people have PTSD, about the same rate as in typical children. If that were true, Kerns points out, PTSD would be one of the only psychiatric conditions that’s no more common in people with autism than in their typical peers.

One potential explanation, Kerns says, is that, like other psychiatric conditions, PTSD simply looks different in people with autism than it does in the general population. “It seems possible to me that it’s not that PTSD is less common but potentially that we’re not measuring it well, or that the way traumatic stress expresses itself in people on the spectrum is different,” Kerns says. “It seemed we were ignoring a huge part of the picture.”

Kerns and a few other researchers are trying to get a better understanding of the interplay between autism and PTSD, which they hope will inform and shape treatment for young people like Gabriel. The more they dig in, the more these researchers are finding that many autistic people might have some form of PTSD. “We’re all just trying to put together the pieces and recognize that it’s an important area that requires further study,” she says. “It’s been a call to arms for the field to start looking at this.”

These researchers have their work cut out for them. In the typical population, PTSD is fairly well defined. According to the Diagnostic and Statistical Manual of Mental Disorders, or DSM-5, psychiatry’s guide to diagnoses, PTSD usually develops after someone sees or experiences a terrifying or life-threatening event. After that initial episode, any reminder of it can trigger panic, extreme startle reflexes and flashbacks. Beyond that, however, there’s a wide variety in the way PTSD manifests: It can lead to hypervigilance and anger; it can cause recurring nightmares and other sleep issues; or it can lead to depression, persistent fear, aggression, irritability or difficulty concentrating and remembering things.

“If you do the math, according to the PTSD criteria in the DSM-5, you can have 636,000 different combinations of symptoms that that describe PTSD,” says Danny Horesh, head of the Trauma and Stress Research Lab at Bar-Ilan University in Ramat Gan, Israel. Given all the traits in people with autism that may overlay these permutations, “you have a lot of reason to think that their version of PTSD might be very different,” he says.

Preliminary studies are just beginning to confirm that idea and to show that what constitutes trauma may be different in people on the spectrum. Together with Ofer Golan, an autism expert at Bar-Ilan, and others, Horesh has begun investigating where PTSD and autism converge. The group has recruited upwards of 130 participants, including students and some people diagnosed with autism, and tried to determine where they fall on the spectrum and whether they have any traditional signs of PTSD.

Abuse, sexual assault, violence, natural disasters and wartime combat are all common causes of PTSD in the general population. Among autistic people, though, less extreme experiences — fire alarms, paperwork, the loss of a family pet, even a stranger’s offhand comment — can also be destabilizing. They can also be traumatized by others’ behavior toward them.

“We know from the literature that individuals with autism are much more exposed to bullying, ostracizing, teasing, etc.,” Golan says. “And when you look in the clinic, you can see that they’re very sensitive to these kinds of events.” Among autistic students, Golan and Horesh have found, social incidents, such as ostracizing, predict PTSD more strongly than violent ones, such as war, terror or abuse, which are not uncommon in Israel. Among typical students, though, the researchers see the opposite tendency.

Given these differences, and the communication challenges autistic people often have, their PTSD can be particularly difficult to recognize and resolve.

“It’s so absurd that there are such excellent treatments for autism today, and such excellent treatments for PTSD today, and so much research on these interventions. But no one to date has connected both,” Horesh says. “How do you treat PTSD in people with autism? No one really knows.”