Research from a California study has found fatal opioid overdoses are more common among people taking anti-anxiety drugs, such as clonazepam or lorazepam. The study, published in the British Medical Journal yesterday, found 30 per cent of all fatal opioid overdoses in the U.S. also involved benzodiazepines. Benzos, a class of drugs usually used to treat anxiety and sleep problems, have been abused even since their invention. This study, however, is the first large study to analyze the relationship between benzo use and opoiod overdoses.

The research, done at Stanford University and the University of California, analyzed information from 315,428 privately insured people aged 18 to 64. The criteria for analysis was simple – the user needed to have an opioid prescription and be  continuously enrolled in a health plan with medical and pharmacy benefits. The people being monitored had no previous drug addictions and had  had been prescribed these drugs by a physician, according to lead author Dr. Eric Sun, assistant professor at the department of anesthesiology, pain and perioperative medicine at Stanford University in California. Many opioid users ended up in the hospitals with dangerous opioid OD’s.

In general, the study found an increase of the painkillers in combination with anti-anxiety drugs in the period from 2001 to 2013.  In 2001, 9% opioid users were using benzodiazepines, but by 2013, the number had increased to 17%. Those who took both drugs together had a much higher risk of death than people using one drug on a regular basis.

Substance abuse is common among people with anxiety disorders, especially those seeking relief from symptoms of disorders like PTSD. At first, for many people, abusing a drug helps lessen their social anxiety. After a while, however, drug abuse can cause a tolerance for the substance, making the user anxious when they can’t get ahold of their drug of choice. Many users will then move on to stronger drugs or take drugs in combination to get relief.

Fatal opioid OD’s occur because both benzodiazepines and opioids (including synthetic opiates) suppress the respiratory system, causing the user to stop breathing. While those in the medical community are aware of this effect, many users aren’t. A “black box” warning on both opioids as well as benzos issued by the U.S. Food and Drug Administration has been created to help users understand the risks better.

Dr. Eric Sun believes that fatal overdoses could be reduced by up to 15% if doctors stopped prescribing opioids and anti-anxiety drugs together.

“Probably most clinicians are aware of the increased risk — they might not be aware of the magnitude,” he told CBC Radio Canada.