Remembering a sequence of numbers or spatial locations became harder—and required more mental effort—when healthy young adults completed the tasks while breathing a carbon-dioxide mixture designed to induce acute anxiety.
Warren Dunger, Marc Edwards, Alex Board and Matthew Garner of the University of Southampton used a controlled 7.5 percent carbon-dioxide challenge to examine how panic-like bodily sensations affect verbal and visuospatial working memory. Their study was published in Human Psychopharmacology: Clinical and Experimental.
The final sample included 30 healthy adults between 18 and 26 years old, 25 of whom were female. Each participant attended two laboratory sessions separated by at least seven days, inhaling the carbon-dioxide mixture during one and ordinary medical air during the other.
The order was randomized and participants were initially unaware of which condition they were receiving, although 28 of the 30 correctly identified the order when they were debriefed. That high recognition rate illustrates how noticeable the carbon-dioxide challenge can be.
A 7.5 percent carbon-dioxide mixture temporarily creates physical and emotional sensations associated with anxiety, including air hunger, altered breathing, increased heart rate and feelings of alarm. Researchers use it as a supervised experimental model because it can induce a brief, repeatable state without relying on a threatening image or a difficult social situation.
Two minutes after inhalation began, participants completed standardized paper-based assessments. The battery included a task requiring mental switching, verbal exercises involving forward, backward and reordered number sequences, and spatial tasks requiring participants to remember locations.
The carbon-dioxide condition reduced spatial working-memory performance. It also reduced accuracy on verbal working-memory tasks when the cognitive load was high, such as holding information in mind while reversing or reorganizing it.
Participants reported greater effort across the verbal and spatial tests during the carbon-dioxide condition. When the researchers combined accuracy and effort into a measure of processing efficiency, performance was worse under experimentally induced anxiety.
That distinction matters. Someone can sometimes preserve an acceptable test score by exerting considerably more mental effort. Looking only at the final number may miss the additional cognitive burden created by anxiety.
Working memory is the limited mental workspace used to retain and manipulate information over short periods. It is involved when following multi-step instructions, calculating mentally, navigating unfamiliar surroundings or keeping track of a conversation while deciding how to respond.
Acute respiratory alarm can compete for those resources. Attention turns toward breathing, heartbeat and the possibility of danger, leaving less capacity available for another demanding task. The study gives researchers a controlled way to examine that interference.
Its clinical relevance concerns how cognitive tests are interpreted. A patient who is highly anxious during a neuropsychological assessment may perform below their ordinary ability or require unusual effort to maintain performance. The authors therefore encourage clinicians to assess anxiety when interpreting tests of working memory.
The experiment does not show that anxiety explains every low memory score. Neurological illness, medication, sleep, pain, language, education and many other factors can affect performance. Anxiety is one influence that may need to be considered rather than automatically treated as irrelevant to the test.
The study’s sample was small, young and predominantly female. Results from healthy university-age adults cannot be assumed to apply directly to older patients, people with neurological conditions or those living with panic disorder.
A laboratory carbon-dioxide challenge also differs from a spontaneous panic attack. Participants knew they were in a supervised experiment, the exposure was controlled and the symptoms occurred without the personal history or situational meaning that can shape naturally occurring anxiety.
This method should not be confused with ordinary indoor carbon-dioxide exposure, breathwork or a home experiment. The concentration, participant screening, equipment and continuous supervision are essential parts of the research design.
The study’s most useful conclusion is that “not thinking clearly” during acute anxiety can be measured as more than a subjective complaint. The next question is whether treatment that reduces fear of bodily sensations also protects working-memory efficiency—and whether cognition recovers at the same rate as the feeling of respiratory alarm.
