June 22 (UPI) -- Young adults who use marijuana daily are more likely to have suicidal thoughts, plan a suicide attempt or attempt suicide than non-users, an analysis published Tuesday by JAMA Network Open found.
Among adults age 18 to 34 with a history of depression who reported using the drug daily or nearly every day, 56% said that they had had thoughts of suicide, or suicidal ideation, the data showed.
In comparison, 44% of those with a history of depression who used marijuana less frequently reported thoughts of suicide.
Both of these figures are higher than the 38% of non-users who had a history of depression and reported having suicidal thoughts.
However, the researchers said the findings do not necessarily suggest that marijuana causes suicidal thoughts among those with depression -- though any potential links should be investigated.
This, they said, is particularly important as more states legalize the drug for medicinal and recreational use, and as some physicians prescribe it for depression treatment.
"We've seen a very significant rise in marijuana use among young adults in this country," study co-author Dr. Nora D. Volkow told UPI in a phone interview.
"And, we need people to understand the potential negative consequences of this use," said Volkow, who s director of the National Institute on Drug Abuse.
The findings are based on an analysis of data on nearly 282,000 adults age 18 to 34 in the United States from 2008 through 2019.
The researchers tracked participants' marijuana use, as well as suicidal ideation and planned and attempted suicide.
Among daily or near-daily users with no history of depression, 9% reported suicidal ideation in the previous year in 2018-19, compared with 7% of more infrequent users and 3% of non-users, the data showed.
Meanwhile, 22% of daily or near-daily marijuana users with a history of depression reported that they had planned a suicide attempt in the past year, compared with 17% of less frequent users and 13% of non-users.
Of those without a history of depression, 2% of daily or near-daily users attempted suicide, compared with just under 2% of more infrequent users and slightly less than 1% of non-users.
Similarly, 8% of all daily marijuana users reported attempting suicide in the previous year in 2018-19, compared with 9% of less frequent users and 5% of non-users.
Although suicide rates declined in the United States and around the world in 2020, they remained higher nationally last year than in 2000, according to the Centers for Disease Control and Prevention.
Over the same period, 33 states have legalized the use of marijuana, or cannabis, for medical purposes, when prescribed by a physician, while 16 now allow recreational use of the drug.
Rates of suicidal ideation were 40% higher among marijuana users in 2018-19 than they were 10 years earlier, researchers found.
In addition, planned suicide attempts and suicide attempts among users were 40% and 60% higher, respectively, they said.
The relationship between marijuana use and suicide risk remains unclear, though research has suggested that there are common "genetic factors" between cannabis use disorder, or problem use, and severe depression, according to Volkow.
Frequent alcohol use has also been linked with depression, "but does not have the level of impact" found with marijuana in this study, she said.
"As more and more states legalize marijuana, they need to know what potential adverse consequences there are to marijuana use, particularly in those who are already vulnerable to mental illness," Volkow said.