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The prevalence of prescription, over-the-counter, and illicit drugs found in the bodies of pilots killed in aviation accidents has continued to trend upwards in recent years, according to a new study from the National Transportation Safety Board (NTSB).
The study is a follow-up to a similar one published in 2014, which examined toxicology results from pilots killed in aviation accidents between 1990 and 2012. For the new study, investigators analyzed results from pilots who died in aviation accidents — including helicopter crashes — between 2013 and 2017, mostly in general aviation operations.
Toxicology test results were available for 952 pilots who were fatally injured in the United States between 2013 and 2017. Of these, more than a quarter — 28 percent — tested positive for at least one potentially impairing drug, up from 23 percent in the 2014 study.
Fifteen percent were positive for at least one drug indicating a potentially impairing condition, i.e., an underlying medical condition that could affect their performance. That represented an increase of three percentage points from 2014.
Moreover, 10 percent showed evidence of use of at least one controlled substance, compared to about eight percent previously. About five percent tested positive for an illicit drug, a slight increase from the less than four percent in the 2014 study.
In a report published on March 10, the NTSB notes that a positive toxicology finding doesn’t necessarily indicate that the pilot was impaired at the time of the crash. However, the analysis included some cases where drug use was explicitly identified as a contributing factor to the accident, such as the June 2015 crash of a cropdusting helicopter whose pilot was found to have been chronically taking high doses of hydrocodone, an opioid pain reliever.
Hydrocodone was one of the three most common drugs in the study indicating a potentially impairing condition. The others were citalopram, an antidepressant; and diazepam, used to treat anxiety and muscle spasms.
Some drugs were classified as potentially impairing without necessarily indicating a chronic medical condition. Of these, sedating antihistamines were the most common category, found in 11.9 percent of pilots in the study — up from 9.9 percent in 2014.
Just as it had in the previous study, the NTSB found no reliable relationship between evidence of drug use and the circumstances of the fatal accidents.
“Further research may identify increased accident risk associated with some drugs or combinations of drugs, which would support improved guidance or limitations on use of those drugs while flying,” the NTSB’s report states. “Conversely, some drugs believed to be ‘potentially impairing’ may not be correlated with accident risk and concerns about their specific effects may be reduced.”