Fact-check: Did a study show that 70% of veterans who committed suicide had THC in their system?
Austin American-Statesman - 7/15/2019
Texas lawmakers this year voted to broaden the state's medical marijuana program to include more qualifying conditions than just intractable epilepsy.
Under the bill, which was signed into law, patients with several more conditions, including terminal cancers, autism and multiple sclerosis, will now be eligible to participate in the program.
During a debate in the Senate over the proposal, state Sen. Donna Campbell, R-New Braunfels, argued against including post-traumatic stress disorder in the bill. The disorder was ultimately not included in the bill that passed.
"A study was done, a post-mortem, so a retrospective study done, looking at autopsies and drug levels, what drugs were in the blood of veterans that committed suicide, and 70 percent had THC," Campbell said.
We decided to take a look at Campbell's claim to see if a study of this nature existed and whether there's a connection between veterans, marijuana use and suicide.
No signs of Campbell's study
Campbell's office did not respond to multiple requests for comment. We searched far and wide but could not find a study with results matching those described by Campbell.
Several experts and advocates contacted for this piece said they were unaware of a study that reflected the findings Campbell described.
Several studies examine the relationship between cannabis use and suicidal thoughts. Others have cross-referenced registry data on deaths attributed to suicide with the timing of the legalization of medical marijuana in the states where the suicides took place.
Dr. Arpana Agrawal, professor of psychiatry at the Washington University School of Medicine who authored a study on cannabis and suicidal thoughts and behavior, said these types of studies have produced mixed results.
In her study, which enlisted identical twins, one of whom used cannabis more frequently and the other who used it lightly or not at all did not use it all or lightly, found that the twins that used cannabis more often were more likely to report suicidal thoughts and depression.
While the data suggests that the association is unrelated to shared genetics and early environment, it does not necessarily mean that the effects of cannabis were the cause, she said. It could have been another risk factor, such as trauma.
A 2016 study by CDC scientists that used data from the National Survey on Drug Use and Health found that the rate of suicidal thinking was more than nine times higher for veterans with drug problems than those without, with the majority involving marijuana abuse.
The study noted, however, that other factors, such as coping with post-traumatic stress, managing chronic pain conditions related to war injuries, or adjusting to civilian life, could confound the association between the two.
What makes this subject so hard to study? Agrawal said one reason is that suicide is such a complex behavior with many aspects -- from contemplation, to attempts (with or without a plan) to actual deaths.
"(Researchers) might have asked only of individuals who report experiencing depression, although suicidal thoughts and behaviors are not just limited to depression," Agrawal said. "In studies of completed suicide, little may be known about the substance use history over and above a toxicology report."
Cannabis use and veterans
Research also is lacking on cannabis use and suicide among veterans specifically.
A study conducted by Safe States Alliance, an injury and violence prevention national nonprofit, in March 2018 used data from the Centers for Disease Control and Prevention's National Violent Death Reporting System to analyze U.S. veteran and armed forces deaths from suicide.
The group's study found that 9 percent of victims had marijuana in their system. It did not show whether a victim had more than one substance in their system.
Sharon Gilmartin, deputy director of Safe States Alliance, said she wasn't aware of a statistic like the one Campbell cited.
Gilmartin also cautioned against interpreting her organization's studies or others that include toxicology data as definitively linking marijuana to suicide because of the nature of THC.
"It's not quite like alcohol where you have a certain BAC (blood alcohol content), and that directly links to impairment, then it goes away and you're kind of back to sobriety more or less," Gilmartin said. "When you think about THC, it's a different dose-response relationship, and it also has a different latency period, so it stays in your blood long after you're impaired."
There are also limitations to what such data can tell us, Agrawal said, because of that age-old statistical standard that "correlation does not imply causation."
"While such studies show a correlation, it is difficult to know from data at one time point whether cannabis use is a causal factor," Agrawal said. "Veterans are more likely to report cannabis use and are also at risk for suicide. But that doesn't answer the question as to how the two are related."
For example, she said, people who are vulnerable to suicide might use cannabis more often to self-medicate; or people who use cannabis more heavily may report more suicidal thoughts; or alternatively, some other factor might influence the use of both cannabis and risk for suicide, such as trauma exposure.
Campbell suggested that cannabis plays a role in suicide among veterans, claiming that a study showed 70 percent of veterans who committed suicide had THC in their body.
But the study Campbell cited doesn't seem to exist. Some research does exist on this topic, but experts questioned the validity of drawing a conclusion about the connection between marijuana use and suicide generally -- let alone among veterans
We rate this claim Pants on Fire.
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