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Half of adults with ADHD have had a substance use disorder — Canadian study

Half of adults aged 20-39 with attention deficit hyperactivity disorder (ADHD) have had a substance use disorder in their lifetime, according to University of Toronto research published in the journal Alcohol and Alcoholism. This is markedly higher than the 23.6% of young adults without ADHD who have had a substance use disorder in their lifetime.

The following material was published by the University of Toronto on 31 August 2021.

Even after considering factors such as age, race, income, education, childhood adversities and other mental illness, young adults with ADHD were still 69% more likely to have had a substance use disorder when compared to their peers without ADHD.

Controlling for lifetime history of mental illness and childhood adversities caused the largest attenuation of the ADHD-substance use disorder relationship.

More than one-quarter (27%) of those with ADHD had a history of depression, which was much higher than the prevalence among those without ADHD (11%).

“These results emphasise the importance of addressing depression and anxiety when providing care to those with co-occurring ADHD and substance use disorder,” reported lead author Dr Esme Fuller-Thomson, Professor in the University of Toronto’s Factor-Inwentash Faculty of Social Work and Director of the Institute for Life Course and Ageing.

“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.”

Those with ADHD also experienced high levels of adverse childhood experiences, with more than a third of young adults (35%) reporting that they had been physically abused and one in nine reporting that they were a victim of sexual abuse (11%) before the age of 16.

A strong association between childhood adversities and substance use disorder has been found in previous research as well.

“Childhood maltreatment may disrupt emotional regulation and the neuro-development of children, which may predispose them to later developing substance dependence,” says co-author Danielle Lewis, a graduate of the University of Toronto’s Masters of Social Work Programme.

Alcohol use disorders were the most common substance abuse disorders among young adults with ADHD (36%), followed by cannabis use disorders (23%). Young adults with ADHD were also three times more likely to experience an illicit drug disorder (other than cannabis) when compared to their peers without ADHD (18% vs 5%).

“One potential explanation for the extremely high rate of illicit drug use among those with ADHD is the accelerated gateway hypothesis,” said co-author Senyo Agbeyaka, a recent University of Toronto MSW graduate who is a social worker at University Health Network.

“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.”

The data were drawn from the Canadian Community Health Survey-Mental Health, a nationally representative sample of 270 respondents aged 20 to 39 with ADHD and 6,602 without ADHD.

The findings of the study underline the extreme vulnerability of young adults with 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


Study details

Attention-Deficit/Hyperactivity Disorder and Alcohol and Other Substance Use Disorders in Young Adulthood: Findings from a Canadian Nationally Representative Survey

Esme Fuller-Thomson, Danielle A Lewis and Senyo Agbeyaka

Author affiliations: University of Toronto and Toronto General Hospital.

Published in Alcohol and Alcoholism on 3 August 2021




(a) To document the prevalence and odds of (i) alcohol use disorders, (ii) cannabis use disorders, (iii) other drug use disorders and (iv) any substance use disorder (SUD), among young adults with and without ADHD, and (b) to investigate the degree to which the association between ADHD and SUDs is attenuated by socio-demographics, early adversities and mental health.


Secondary analysis of the nationally representative Canadian Community Health Survey-Mental Health (CCHS-MH). The sample included 6872 respondents aged 20–39, of whom 270 had ADHD. The survey response rate was 68.9%.


Substance Use Disorder: World Health Organization’s Composite International Diagnostic Interview criteria, SUDs, were derived from lifetime algorithms for alcohol, cannabis and other substance abuse or dependence. ADHD was based on self-report of a health professional’s diagnosis.


One in three young adults with ADHD had a lifetime alcohol use disorder (36%) compared to 19% of those without ADHD (P < 0.001).

After adjusting for all control variables, those with ADHD had higher odds of developing alcohol use disorders (OR = 1.38, 95% CI: 1.05, 1.81), cannabis use disorders (OR = 1.46, 95% CI: 1.06, 2.00), other drug use disorders (OR = 2.07, 95% CI: 1.46, 2.95) and any SUD (OR = 1.69, 95% CI: 1.28, 2.23).

History of depression and anxiety led to the largest attenuation of the ADHD-SUD relationship, followed by childhood adversities and socioeconomic status.


Young adults with ADHD have a high prevalence of alcohol and other SUDs. Targeted outreach and interventions for this extremely vulnerable population are warranted.


University of Toronto material – New research by Esme Fuller-Thomson finds that half of adults with ADHD have had a substance use disorder (Open access)


Alcohol and Alcoholism article – Attention-Deficit/Hyperactivity Disorder and Alcohol and Other Substance Use Disorders in Young Adulthood: Findings from a Canadian Nationally Representative Survey (Restricted access)


See also from the MedicalBrief archives


Genetic variants that increase ADHD risk discovered


Using MRI to detect ADHD


Prescription drug misuse starts early


Diagnosis of ADHD ‘spreading like a contagion’




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