Cannabis Tied To Self-Harm, All-Cause Mortality In Youth With Mood Disorders

Youth with mood disorders are at increased risk for self-harm and all-cause mortality when they also have cannabis use disorder, a new study suggests.

Researchers examined Ohio Medicaid claims data on 204,780 youth aged 10 to 24 years who had been diagnosed with mood disorders between July 1, 2010 and December 31, 2017 to see if risk of self-harm or all-cause mortality within one year of any cannabis use disorder diagnosis was increased. Overall, a total of 21,040 (10.3%) of the youth in the study had cannabis use disorder.

Over the one-year period after the index date of cannabis use disorder diagnosis, youth with this condition were at significantly higher risk for nonfatal self-harm (adjusted hazard ratio 3.28) and all-cause mortality (aHR 1.59) compared to those without a cannabis use disorder diagnosis during the same period.

"In the short term, among youths who are vulnerable to suicidal behavior, cannabis may increase the likelihood that they were acting on it because cannabis is associated with greater impulsivity, poor judgment and clouded thinking," said lead study author Cynthia Fontanella, an associate professor in psychiatry and behavioral health at the Ohio State University Wexner Medical Center in Columbus.

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"In the long term, ongoing daily cannabis use can impact management of mood disorders," Fontanella said by email.

Heavier cannabis use can also moderate the course of conditions like bipolar disorder by increasing time to recovery, relapse, and recurrence of manic episodes as well as psychotic symptoms, Fontanella added.

While cannabis use disorder wasn't significantly associated with an increased risk of death by suicide, it was linked to a significantly higher risk of death by unintentional overdose (aHR 2.40) and homicide (aHR 3.23).

The risk of comorbid cannabis use disorder in youth with mood disorders increased with age, the researchers report in JAMA Pediatrics.Compared with participants aged 10-13 years, cannabis use disorder was significantly more likely in those aged 14-18 (aHR 9.35) and 19-24 (aHR 11.22).

Cannabis use disorder was also significantly more common among youth with a history of psychiatric hospitalizations (aHR 1.66) and mental health emergency department visits (aHR 1.54).

For some youth, cannabis may be a coping mechanism, said Dr. Sharon Levy, director of the Adolescent Substance Use and Addiction Program at Boston Children's Hospital.

"In my clinical experience, many teens with cannabis use disorder have come to rely on cannabis use as a strategy, sometimes their only strategy, when they are feeling sad or stressed," Dr. Levy, who wasn't involved in the study, said by email.

"While use may offer immediate relief it can also do harm, both in the long term by making the depression worse, and, as this study points out, in the short term as well by increasing the risk of self-harm," Dr. Levy said.

One limitation of the study is the potential for cannabis use disorder to be underdiagnosed, the study team notes. Results from Medicaid claims in Ohio also may not be representative of all youth with mood disorders or cannabis use disorder.

Even so, the results underscore the importance of clinicians asking patients about any drug use, including cannabis as well as tobacco and alcohol, said Dr. Koen Bolhuis, a researcher in the department of Child & Adolescent Psychiatry/Psychology at Erasmus Medical Center Rotterdam in the Netherlands.

"Use of these substances is associated with all sorts of bad medical outcomes, but also negatively affect treatment response of their psychiatric problems," Dr. Bolhuis, who wasn't involved in the study, said by email. "If the clinician doesn't trust whether the young person tells the truth about their substance use, significant others such as friends, partners or even parents/caregivers should be included in the assessment."

—Lisa Rapaport

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