By Emily Giblett
Research conducted by psychologists at University College London has found a link between inhalation of laughing gas and the long-term formation of distressing memories.
The study, findings of which were published in the journal Psychological Medicine, required 50 healthy adult participants to watch distressing scenes from a film and measure the frequency of intrusive thoughts that they experienced in the week following the screening.
The film clips used in the experiment were from Gaspar Noe’s 2003 thriller Irréversible, described by one critic at its release as “so violent and cruel that most people will find it unwatchable.” Participants were asked to watch two clips of a brutal and violent nature from the film, one of which involved a character being beaten with a fire extinguisher. This film was chosen as it has been shown to replicate a milder form of trauma created after real-life events.
Immediately after being shown the film clips, half the group spent 30 minutes inhaling an equal mixture of laughing gas (nitrous oxide) and oxygen. Data showed that the group that had inhaled the nitrous oxide mixture experienced less intrusive thoughts following the experiment, with their memories of the traumatic scenes declining steeply over the week. In contrast, the decline in the frequency of intrusive thoughts for the group that did not inhale nitrous oxide following their viewing was noticeably more gradual.
The effects upon memory formation could be due to the impact of laughing gas upon receptors in the brain. Speculating upon the chemical basis for the connection between nitrous oxide and memory formation, lead author Dr Ravi Das said, “we think nitrous oxide disrupts a process that helps permanent memories to form’.
N-methyl-D-aspartate [NMDA] receptors exist to tag information collected throughout the day which is then filed during sleep. Nitrous oxide blocks these receptors, and is thus believed to interfere with the formation of memories.
Research also found that participants who felt more ‘dissociated’ experienced a higher frequency of intrusive thoughts. Signs of dissociation, measured in the study by questionnaire, can include a feeling of disconnection from your body, the sensation that your experiences are unreal and a distorted understanding of time. This may sound familiar to those who have used laughing gas recreationally, as nitrous oxide can produce a similar experience. Presentation of dissociated feelings in individuals during and after trauma can be an early warning sign of Post-Traumatic Stress Disorder [PTSD].
Nitrous oxide is often used by paramedics and in childbirth as short-term pain relief. Whether the gas can be used to alleviate the symptoms of PTSD is as yet unclear and may depend on how dissociated a patient feels prior to nitrous oxide being administered.
Dr Das stressed that the amount of laughing gas inhaled recreationally from a balloon would be “too small to have a noticeable effect on memory formation.” Further research is required to ascertain whether other medicines such as Ketamine have a similar effect on memory.