Much like its sister-in-initials OCD, ADHD, or attention deficit hyperactivity disorder, is one of those conditions people can sometimes treat like a fun personality quirk. In fact, it can be a seriously debilitating disorder: sufferers can struggle with schoolwork and social interaction, and those who do manage to navigate the world often need a long list of coping mechanisms to get them through the day.

So the results of a new study published this week in the journal Alcohol and Alcoholism are perhaps understandable: according to the research, young adults with ADHD are more than twice as likely as their peers without the condition to have had a substance use disorder in their lifetimes. And the biggest risk factor for a substance use disorder? A history of anxiety and depression – which ADHD sufferers are nearly three times more likely to experience.

“These results emphasize the importance of addressing depression and anxiety when providing care to those with co-occurring ADHD and [substance use disorders],” said lead author Esme Fuller-Thomson. “Individuals with untreated depression and anxiety may self-medicate to manage the symptoms of an untreated psychiatric disorder, which can result in greater substance use.”

The researchers analyzed data from the Canadian Community Health Survey-Mental Health (CCHS-MH), a nationally representative survey run by Statistics Canada, which gave them a very healthy sample size of more than 6,800 people. Of those, 207 had ADHD – only three percent. But among that small section, more than one in three had a history of alcoholism, nearly one quarter reported a history of cannabis use disorders, and nearly one in five had a history of other drug abuse.

“One potential explanation for the extremely high rate of illicit drug use among those with ADHD is the accelerated gateway hypothesis,” explained study co-author Senyo Agbeyaka. “This theory posits that people with ADHD tend to initiate substance use at a younger age, resulting in riskier use and greater problem severity in adulthood.”

One reason for those early introductions to drug abuse is simple: it’s an attempt to manage the symptoms of the condition. In a 2017 interview about her severe ADHD, Eliana Letzter described how, by high school, she had “turned to marijuana, really heavy marijuana use.” It didn’t fix her symptoms, she explained, but it “sort of mutes them and dampens them.”

After that, she became addicted to amphetamines – and the effect they had on her condition.

“To a large extent what I became addicted to was the ability to write,” she said. “I would take [pills] in order to be able to write for extended periods, or read things. But because I wasn't in a healthy environment and I wasn't in a healthy mental state, it got real bad.”

But another reason for the higher levels of substance abuse among those with ADHD is even more heartbreaking: more than one third reported experiencing physical abuse as a child, and one in nine said they had suffered childhood sexual abuse.

“Childhood maltreatment may disrupt emotional regulation and the [brain] development of children,” said co-author Danielle Lewis in a statement. “[That] may predispose them to later developing substance dependence.”

Even that, though, is not the whole story. When the researchers controlled for a variety of risk factors – age, race, income, education, and the two with the biggest impacts, childhood adversities and mental illness – people with ADHD were still 69 percent more likely to have had a substance use disorder in their history than somebody without ADHD.

“There is a clear need to develop prevention and treatment programs to address substance use issues among those with ADHD, while also promoting mental health and addressing childhood adversities.” said Fuller-Thomson.