Young adults who use cannabis ― either sporadically, daily, or those who have cannabis use disorder ― have a significantly increased risk for suicidal thoughts and actions, according to US national drug survey data.
The risks appear greater for women than men and remained regardless of whether the individual was depressed.
“We cannot establish that cannabis use caused increased suicidality,” Nora Volkow, MD, director, National Institute on Drug Abuse (NIDA), told Medscape Medical News.
“However, it is likely that these two factors influence one another bidirectionally, meaning people with suicidal thinking might be more vulnerable to cannabis use to self-medicate their distress, and cannabis use may trigger negative moods and suicidal thinking in some people,” said Volkow.
“It is also possible that these factors are not causally linked to one another at all but rather reflect the common and related risk factors underlying both suicidality and substance use. For instance, one’s genetics may put them at a higher risk for both suicide and for using marijuana,” she added.
The study was published online June 22 in JAMA Network Open.
Marked Increase in Use
Cannabis use among US adults has increased markedly over the past 10 years, with a parallel increase in suicidality. However, the links between cannabis use and suicidality among young adults are poorly understood.
NIDA researchers sought to fill this gap. They examined data on 281,650 young men and women aged 18 to 34 years who participated in National Surveys on Drug Use and Health from the 2008 to 2019.
Status regarding past-year cannabis use was categorized as past-year daily or near-daily use (≥300 days), non-daily use, and no cannabis use.
Although suicidality was associated with cannabis use, even young adults who did not use cannabis on a daily basis were more likely to have suicidal thoughts or actions than those who did not use the drug at all, the researchers found.
Among young adults without a major depressive episode, about 3% of those who did not use cannabis had suicidal ideation, compared with about 7% of non-daily cannabis users, about 9% of daily cannabis users, and 14% of those with a cannabis use disorder.
Among young adults with depression, the corresponding percentages were 35%, 44%, 53%, and 50%.
Similar trends existed for the associations between the different levels of cannabis use and suicide plan or attempt.
Women at Greatest Risk
Gender differences also emerged. Women who used cannabis at any level were more likely to have suicidal ideation or report a suicide plan or attempt than men with the same levels of cannabis use.
Among those without a major depressive episode, the prevalence of suicidal ideation for those with vs without a cannabis use disorder was around 14% vs 4.0% among women and 10% vs 3.0% among men.
Among young adults with both cannabis use disorder and major depressive episode, the prevalence of past-year suicide plan was 52% higher for women (24%) than for men (16%).
“Suicide is a leading cause of death among young adults in the United States, and the findings of this study offer important information that may help us reduce this risk,” lead author and NIDA researcher Beth Han, MD, PhD, MPH, said in a news release.
“Depression and cannabis use disorder are treatable conditions, and cannabis use can be modified. Through better understanding the associations of different risk factors for suicidality, we hope to offer new targets for prevention and intervention in individuals that we know may be at high risk. These findings also underscore the importance of tailoring interventions in a way that take sex and gender into account,” said Han.
“Additional research is needed to better understand these complex associations, especially given the great burden of suicide on young adults,” said Volkow.
Gender Difference “Striking”
Commenting on the findings for Medscape Medical News, Charles B. Nemeroff, MD, PhD, professor and chair, Department of Psychiatry and Behavioral Sciences, Dell Medical School, University of Texas at Austin, said this study is “clearly of great interest; of course correlation and causality are completely distinct entities, and this study is all about correlation.
“This does not, of course, mean that cannabis use causes suicide but suggests that in individuals who use cannabis, suicidality in the broadest sense is increased in prevalence rate,” said Nemeroff, who serves as principal investigator of the Texas Child Trauma Network.
Nemeroff said “the most striking finding” was the larger effect in women than men ― “striking because suicide is in almost all cultures higher in prevalence in men vs women.”
Nemeroff said he’d like to know more about other potential contributing factors, “which would include a history of child abuse and neglect, a major vulnerability factor for suicidality, comorbid alcohol and other substance abuse, comorbid psychiatric diagnosis such as posttraumatic stress disorder.”
The study was sponsored by NIDA, of the National Institutes of Health. Volkow, Han, and Nemeroff have disclosed no relevant financial relationships.
JAMA Netw Open. Published online June 22, 2021. Full text