Sleep loss may fuel anxiety by clogging threat adaptation: Study

A lack of sleep may heighten anxiety by impairing the brain's ability to adapt to new, potentially threatening environments, keeping individuals in a persistent state of hypervigilance, according to a recent study.

Previous research has linked sleep deprivation to heightened activity in brain regions involved in anxiety, such as the amygdala, showing that emotional centers are over 60% more active following a sleepless night, reports the NewScientist.

However, earlier studies typically exposed participants to negative stimuli for only a few seconds at a time.

Addressing how sleep loss affects reactions in more realistic situations, researchers led by Emma Sullivan of the University of Melbourne in Australia examined 54 healthy adults aged 18 to 30 with no history of neurological, psychiatric, or sleep conditions.

In the study, half of the participants remained awake overnight -- verified using sleep trackers -- while the other half slept for eight hours in a laboratory.

The following morning, participants navigated an immersive virtual environment, moving between a bright office with gentle music and a dark basement with ominous music, unsettling sounds, and tasks requiring them to collect lanterns.

Researchers monitored participants' heart rates and skin-conductance levels, which measure subtle changes in sweating associated with the fight-or-flight response.

The findings revealed that while all participants experienced elevated stress upon initially entering the virtual basement, only the well-rested group showed reduced stress levels upon re-entering the space, indicating an ability to acclimatise to an ongoing threat.

In contrast, stress levels among sleep-deprived participants remained consistently high throughout repeated exposures. Sullivan noted that such non-adaptation could result in a state of hypervigilance that, if chronic, may manifest as pathological anxiety.

The study also highlighted physiological factors that might buffer against these effects. When reviewing recordings of their experience, sleep-deprived participants with higher heart rate variability -- a marker of good heart health where intervals between heartbeats naturally fluctuate -- reported lower subjective anxiety despite showing strong physiological stress responses.

Conversely, those with lower heart rate variability reported feeling significantly more anxious. Sullivan suggested that interventions known to boost heart rate variability, such as moderate-to-vigorous exercise, could help mitigate the emotional impact of sleep loss.

Experts noted that sleep loss triggers an evolutionary survival mechanism.

Eti Ben Simon of the University of Texas at Dallas, who was not involved in the study, explained that the body views sleep loss as a cue to activate emergency survival systems -- a "better safe than sorry" adaptation that served ancient humans vulnerable to predators, but is less suited to modern life.

Addressing sleep disruption could prove critical, as about one-third of adults in the West experience sleep issues at least once a week, with anxiety serving as both a cause and a symptom.

Sullivan and Ben Simon emphasised that therapies such as Cognitive Behavioural Therapy can simultaneously improve sleep and anxiety.

Additionally, for individuals unable to avoid sleep loss, such as shift workers or new parents, scheduled recovery sleep or napping may help offset the negative impacts on emotional adaptation.