Young adults with different ADHD symptom profiles face distinct cannabis-related risks

A new study published in the journal Cannabis sheds light on how two core features of attention-deficit/hyperactivity disorder—namely inattention and hyperactivity-impulsivity—relate to specific problems associated with cannabis use in young adults. The findings suggest that inattention symptoms are tied to functional consequences like academic struggles, poor self-care, and memory lapses, while hyperactive-impulsive symptoms may lead indirectly to cannabis dependence through increased consumption.

Cannabis use is widespread among young adults, a population that is both neurologically vulnerable to the effects of cannabis and more likely to use it regularly. This is especially concerning for individuals with ADHD, who are at elevated risk for developing problematic cannabis use. Past research has linked ADHD to higher rates of cannabis use disorder and earlier initiation of cannabis use, but few studies have examined how specific ADHD symptoms—such as inattention versus hyperactivity—relate to the different problems that can stem from cannabis use.

“Since cannabis became legal for non-medical use in Canada, there has been an increase in the number of young adults who report they use cannabis to self-medicate symptoms of physical and mental health conditions,” said study author Jeffrey Wardell, an associate professor of psychology at York University.

“Anecdotally working with this population, we have heard young adults report that cannabis helps them with their symptoms of ADHD. This was somewhat surprising to me because cannabis is known to cause impairments in attention, memory, and other cognitive functions, so I would have guessed that cannabis would make ADHD symptoms worse instead of better. But there is also a range of different ADHD symptoms, so I started to wonder if certain types of symptoms might be more related to cannabis use than others.”

“For example, perhaps young adults who have more of the hyperactivity or impulsive symptoms of ADHD (instead of the inattention/concentration symptoms) might perceive that cannabis helps them to relax and not be so fidgety and restless. While a few studies had been done looking at differential associations between the hyperactive/impulsive symptoms and inattention symptoms with cannabis use, findings were mixed, and no studies looked at how these different ADHD symptoms related to different types of cannabis-related outcomes. So, this is what we sought to uncover with this study.”

Wardell and his colleagues recruited 160 young adults in Toronto, aged 19 to 25, all of whom had a history of regular cannabis use. About 54% of participants met the criteria for cannabis use disorder in the past year, based on a structured clinical interview. To be eligible, participants had to have used cannabis at least twice a month for six months at some point in their lives, and they could not have a history of psychosis or regular use of substances other than cannabis.

Participants completed a battery of self-report questionnaires and interviews during an in-person session. ADHD symptoms were measured using a widely used 18-item adult screening tool, which produces separate scores for inattention and hyperactivity-impulsivity. Cannabis-related consequences were assessed using a detailed questionnaire covering eight domains: social issues, impaired control, negative self-perception, self-care, risky behavior, academic or occupational problems, physical dependence, and blackout or memory impairment. The total amount of cannabis flower consumed over the past 90 days was measured using the Timeline Follow Back interview method, which asked participants to recall their daily usage.

The results suggest that inattention and hyperactivity symptoms relate to cannabis consequences in different ways. Inattention symptoms were directly associated with three specific types of cannabis-related problems: difficulties in academic or occupational functioning, poor self-care, and blackout or memory impairments. These associations were not explained by how much cannabis the individual used, suggesting that the presence of inattention symptoms alone may increase susceptibility to these outcomes.

This pattern may reflect the cognitive demands of daily life. Tasks such as maintaining focus, remembering responsibilities, and sustaining routines may be especially challenging for individuals with high inattention, and cannabis use—known to impair memory and motivation—might exacerbate these difficulties.

By contrast, hyperactivity-impulsivity symptoms were not directly linked to specific cannabis-related problems. However, they were associated with greater cannabis use overall, which in turn predicted higher levels of impaired control, physical dependence, and symptoms of cannabis use disorder. This suggests an indirect pathway: individuals high in hyperactivity-impulsivity may use more cannabis, which raises their risk for these more severe forms of cannabis-related harm.

Interestingly, inattention symptoms were negatively associated with physical dependence and impaired control, but only when taking into account their overlap with hyperactivity-impulsivity symptoms. In other words, when statistical models controlled for the influence of hyperactivity symptoms, individuals with high inattention tended to report fewer problems associated with cannabis dependence. This counterintuitive result points to a suppression effect in the data—where the presence of one correlated symptom (in this case, hyperactivity) may mask the influence of another.

The findings also support the idea that individuals with hyperactive-impulsive tendencies may use cannabis in part as a form of self-medication. Previous studies suggest these individuals often report that cannabis helps reduce restlessness or agitation. However, frequent or heavy use can increase the risk of losing control over consumption, developing physical dependence, or meeting the clinical criteria for cannabis use disorder.

By contrast, individuals with high inattention may not experience cannabis as symptom-relieving. Some studies suggest that people with inattention symptoms view cannabis as ineffective or even detrimental for their symptoms. This may partially explain why they consume smaller quantities, even though they still experience negative outcomes in areas like work, school, and self-care.

“Young adults who have elevated levels of hyperactive/impulsive ADHD symptoms reported consuming larger amounts of cannabis, and this was associated with risk for more severe negative outcomes such as cannabis use disorder, inability to control cannabis use, and cannabis tolerance or withdrawal,” Wardell told PsyPost. “Further, although young adults with elevated inattention symptoms of ADHD did not report using more cannabis, they were still at heightened risk of certain types of negative outcomes of cannabis use such as poorer academic performance, poor self care, and memory impairment.”

“So, the main message I would have for young adults with ADHD is even if they perceive that cannabis may be helping their symptoms, there are still risks for negative outcomes. I would recommend that they talk to their healthcare provider for guidance if they plan to use of cannabis to manage ADHD symptoms.”

Although the study offers new insights into the distinct ways inattention and hyperactivity symptoms relate to cannabis-related harm, some limitations should be noted. The cross-sectional design means that causal conclusions cannot be drawn. It remains unclear whether ADHD symptoms lead to cannabis problems, or whether cannabis use exacerbates ADHD-like symptoms. Longitudinal research would be needed to clarify how these relationships develop over time.

The observed effect sizes were also small. For instance, a one-point increase in hyperactivity symptoms was associated with a one percent increase in some cannabis-related problems. While these are statistically significant relationships, their clinical relevance may be limited.

The study, “Understanding the Relationships between ADHD Symptoms and Cannabis-Related Consequences among Young Adults,” was authored by Claire Minister, Christian S. Hendershot, Matthew T. Keough, and Jeffrey D. Wardell.