Nightmares can be one of the most distressing symptoms of post-traumatic stress disorder (PTSD), a condition that may develop after a person experiences a disaster, serious accident, violence, combat, or another severe trauma. During sleep, people with PTSD may feel as though they are living through the event again in vivid detail. These repeated episodes can cause severe sleep loss and make some people afraid to go to bed.
Available medications often provide limited relief from trauma-related nightmares. Researchers at Charité — Universitätsmedizin Berlin therefore examined whether a prescription drug containing THC, one of the active compounds found in cannabis, could help. The findings, published in Nature Medicine, showed that more than half of the participants responded to the treatment. More than one-third said their nightmares disappeared completely.
Why PTSD Nightmares Are So Difficult to Treat
The effects of a terrifying or life-threatening experience can continue long after the immediate danger has passed. In post-traumatic stress disorder (PTSD), the brain has difficulty processing overwhelming events. The memories may be stored in a way that makes them return involuntarily and without conscious control.
This can happen during the day and at night. While sleeping, people with PTSD may repeatedly relive the trauma until they wake in panic. Antidepressants and medications that lower blood pressure are among the treatments sometimes used, but their effectiveness is limited. They also often do little to relieve the nightmares themselves. Germany has not yet approved a medication specifically for trauma-related nightmares.
Prof. Stefan Röpke studies trauma-related disorders at the Department of Psychiatry and Neurosciences on the Benjamin Franklin Campus of Charité. While exploring possible new treatments, he and his team, working with additional research partners, turned their attention to tetrahydrocannabinol, commonly known as THC. It is the primary psychoactive compound in cannabis.
THC interacts with the body’s endocannabinoid system, which helps regulate sleep, stress, and the way emotional memories are processed. Stefan Röpke explains: “There is evidence suggesting that during REM sleep — the intense dream phases in which the brain processes experiences and regulates emotions — THC reduces dream activity and thereby alleviates nocturnal stress responses.”
Testing Dronabinol for PTSD Nightmares
Cannabis-based medicines are already used in pain treatment, especially when standard therapies do not work well enough or cause intolerable side effects. In Germany, access became easier after the so-called “Cannabis for medical purposes” law went into effect in 2017. The legislation expanded the medical and scientific use of cannabinoids derived from plants or produced synthetically.
For the study, the researchers used Dronabinol, a prescription medication containing THC obtained directly from the cannabis plant and administered as drops. They wanted to find out whether the drug could safely reduce nightmares linked to PTSD.
More than 170 people with post-traumatic stress disorder and frequent, severe nightmares took part. For ten weeks, participants received either Dronabinol or a cannabis-flavored placebo that looked identical. They took the drops each evening before going to bed.
Neither the participants nor the healthcare professionals knew who received the medication and who received the placebo. This double-blind, placebo-controlled design is considered the gold standard for testing medical treatments.
Nightmares Declined More With THC Treatment
At the end of the ten weeks, nightmare severity had fallen significantly more in the Dronabinol group than in the placebo group. On a scale ranging from zero to eight, the average nightmare burden dropped by 3.7 points among participants taking Dronabinol. The placebo group experienced an average decrease of 2.2 points. For the people affected, the difference was clearly noticeable.
“More than a third of the patients treated with Dronabinol reported that they no longer experienced any nightmares after ten weeks. Another 21 percent reported that their nightmare burden had been at least halved,” as Stefan Röpke stated. “And about five out of six patients in the dronabinol group felt their health had markedly improved.”
No Severe Side Effects or Signs of Dependence
The cannabinoid appeared to act specifically on nightmares and sleep rather than on every aspect of PTSD. The researchers could not conclusively show that it reduced the overall severity of post-traumatic stress disorder or any accompanying depression.
Even so, most participants experienced meaningful relief. By interrupting the repeated nighttime reliving of trauma, the treatment allowed many of them to sleep more peacefully.
No severe side effects were reported. Mild and moderate effects, including dizziness, headaches, and increased appetite, occurred more frequently among those receiving Dronabinol. The researchers also found no withdrawal symptoms after participants stopped taking the evening doses at the end of the study.
Future studies will examine whether the treatment remains safe and effective when used for longer periods. Researchers also want to determine whether patients may gradually develop tolerance to the drug.
Charité initiated and led the research. Scientists from the Psychiatric University Clinic of the Charité at St. Hedwig Hospital, the University Medical Center Hamburg-Eppendorf, and the Central Institute for Mental Health in Mannheim also participated. The company Bionorica SE supported the work.
