Is the ‘Ambien Defense’ Total Bullsh*t?

The theory claims people under the influence of the drug—like the Fort Hood shooter—act recklessly or violently with no recollection. But research doesn’t back it up.

04.15.14 9:45 AM ET

Fifteen minutes is all it takes—then peaceful slumber. This is the promise of sleep medications like Ambien and its generic versions, whose billion-dollar sales numbers attest to just how many people rely on that promise. But for some, Ambien hasn’t only meant relief for struggling sleepers, but a possible shield against legal culpability—the so-called Ambien Defense, or the argument that one’s judgment or personality is impaired under the influence of the drug, and that it can cause one to commit crimes while not entirely conscious.

While the Ambien defense has been used as a legal strategy, it remains unclear whether it’s a medically sound one. Does Ambien impair judgment enough to drive one to violent crime?

A brief primer on the drug: the world got to know Ambien when it was first introduced in 1992. At the time, there was little talk of any links to violent behavior. Rather, concerns centered on morning impairment, or the inability to shake off the effects of the drug after a full night’s sleep—rendering Ambien takers potentially dangerous drivers in the morning.

New dosages emerged to address specific patient populations, such as the elderly, those with metabolic issues, women (who tend to process the drug more slowly than men), or those whose sleep issues included sleepwalking or waking up in the middle of the night.

The latest iteration of the Ambien defense arose after the tragic events of April 2, when Spc. Ivan Lopez shot three dead and injured 16 others at Fort Hood military base in Texas before turning the gun on himself. According to investigators, he may have used Ambien before the shooting spree.

Lopez’s case is the latest to be tied to possible use of Ambien, with incidents such as the 2009 deaths of eight people by 45-year-old Robert Stewart in North Carolina and the case of Derek Stansberry, who told a flight crew he was carrying explosives in a plane in 2010, still fresh in people’s minds.

Dr. Cheryl Paradis, a professor of forensic psychology at Marymount Manhattan College and an expert on the drug, thinks it’s improbable, and that there could be confusion here as to what is causing what. “You have to remember, it is the most commonly used sleep aid in the U.S., but reported cases of violence have been very rare,” she said. “It is most likely Ambien is not causing this behavior. It’s just that people who are already having psychological problems are using Ambien.”

The association between Ambien and crime also stems from the correlation between insomnia and depression, she said. “Most people who are committing these kinds of crime are mentally ill,” Paradis said. “Most of them are depressed; depressed people have trouble sleeping.”

Across the Atlantic, Dr. Axel Steiger, director of the sleep laboratory at German research institute Max Planck Society, said he has never even heard of Ambien being linked to violent crime.

“Sleep-driving, cooking, food, talking on the phone, or sex in somnambulistic state, without memory [of the behavior] later, have been reported,” Steiger said. Complex behaviors under the influence of so called benzodiazepinessuch as Rohypnol, popularly known as the “roofie,” and other similar hypnotics to Ambien, are not unheard of, said Steiger.

But paradoxical disinhibition phenomena—in lay terms, excitable behavior when you’re on a drug that is meant to induce the opposite—are rare, he said. Notably, despite Fort Hood shooter Lopez’s highlighted use of Ambien, no one has said he may have been sleepwalking.

“His behavior does not sound like the type of behavior described in Ambien-related events,” said Paradis. “Those are events where people are confused, they go to sleep at night, they wake up, and they are in an altered state. They come downstairs in the morning and they find all the food is out of the refrigerator.”

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An e-mailed statement from Sanofi, the manufacturers of original Ambien—the drug has since been off-patent in the U.S. since 2007, and generic versions abound—said the prescription information it provides to doctors and patients does outline that “visual and auditory hallucinations, abnormal thinking, and behavior changes have been reported, including aggressiveness and out-of-character extroversion, bizarre behavior, agitation, and depersonalization have been reported.”

However, Sanofi is quick to point out, “have been reported” means these were instances documented outside controlled clinical trials, meaning it would have no other data on whether additional influences such as underlying psychiatric or physical illness played a role.

The company cited data from a six-month trial it conducted in which 1.5% (10 out of 669) of patients reported anxiety and agitation, and 1.5% (10 out of 669) reported depression. It cited another study where patients already treated with selective serotonin reuptake inhibitors—a class of antidepressant—were given Ambien. Four broke off Ambien usage after experiencing impaired concentration, continuing or aggravated depression, and manic reaction.

But over “22 billion nights of patient therapy worldwide” (Sanofi’s words) or no, the world’s drug regulators have kept their eye on Ambien. Both the U.S. Food and Drug Administration and the European Medicines Agency’s Pharmacovigilance Risk Assessment Committee have recently asked that the product label be changed to more strongly reflect impaired driving risk, and to recommend that only the minimum effective dose be taken, and only at night. Neither mention the risk of patients developing violent tendencies.

Stewart, the shooter at the North Carolina nursing home, survived to use the Ambien defense—he said he was sleepwalking and could not remember what had happened—but to no avail. Stewart was charged with eight counts of first-degree murder and is serving time at the maximum security Central Prison in North Carolina.

Stansberry, who while aboard Delta Airline Flight 273 in 2010 told the flight crew he was carrying explosives and traveling with falsified documents, was deemed by the U.S. Federal Court in Bangor to have suffered a brief “psychotic break.” The court did not see him as a danger to society and set him free. In a more recent, profiled case, Kerry Kennedy, daughter of Robert F. Kennedy, was found not guilty of drugged driving in February, as she said she mistook Ambien for her thyroid medication.

Stewart and Fort Hood’s Lopez were both thought to be emotionally distraught. Stewart’s violent and obsessive relationship with his estranged wife ended with the death of some of her colleagues. Lopez was in turmoil after the death of his mother last year, and was allegedly upset at his limited leave of absence to attend her funeral. Both were on Ambien.

So were Kennedy and Stansberry—but their cases did not end in tragedy, while others did.

“It is very rarely used as a defense, and very rarely effective,” said Paradis. “While there was that case where Kerry Kennedy had Ambien as a defense successfully, no one was hurt, that’s important. It is more likely to be successful when it is something like that, in a minor traffic violation.”