Dream Recall/Affect and the Hypothalamic-Pituitary-Adrenal Axis

In this concise review, we present an overview of research on dream recall/affect and of the hypothalamic–pituitary–adrenal (HPA) axis, discussing caveats regarding the action of hormones of the HPA axis (mainly cortisol and its free form, cortisol-binding globulin and glucocorticoid receptors). We present results of studies regarding dream recall/affect and the HPA axis under physiological (such as waking) or pathological conditions (such as in Cushing’s syndrome or stressful situations). Finally, we try to integrate the effect of the current COVID-19 situation with dream recall/affect vis-à-vis the HPA axis.

Increased Awakenings From Non-rapid Eye Movement Sleep Explain Differences in Dream Recall Frequency in Healthy Individuals

Background

Dreaming is a universal experience, yet there is considerable inter-individual variability in dream recall frequency (DRF). One dominant model, the “arousal-retrieval” model, posits that intra-sleep wakefulness is required for dream traces to be encoded into long-term storage, essentially proposing that a better memory for dreams underlie increased DRF. A recent study utilizing polysomnography combined with an event-related potentials paradigm, provides direct support for this model by demonstrating increased intra-sleep wakefulness in a healthy population by comparing high frequency recallers (HFRs) and low frequency recallers (LFRs). Another study by the same group demonstrated increased regional cerebral blood flow in regions associated with dream production, supporting the premise that HFRs also may produce more dreams.

Hypotheses

This study investigated the profile of nocturnal awakenings and dream production in healthy HFRs and LFRs. Hypothesis (1a): HFRs will spend significantly more time awake after sleep onset; (1b): HFRs will experience significantly more awakenings across the night, and from rapid eye movement (REM) sleep in particular; (2) HFRs will have significantly higher rates of dream production across the night as measured by REM density.

Methods

We studied two groups of healthy adults: HFRs (n = 19) and LFRs (n = 17) who underwent polysomnographic recordings on two non-consecutive nights.

Results

Hypothesis (1a) was confirmed: HFRs spent significantly more time awake after sleep onset. Hypothesis (1b) was partially confirmed: HFRs experienced significantly more awakenings across the night; however, awakenings from REM sleep were comparable. Interestingly, HFRs had significantly more awakenings, as well as a higher number of longer awakenings, from non-rapid eye movement (NREM) stage 2 sleep. Hypothesis (2) was not confirmed: There was no significant difference in rates of REM density between groups.

Conclusion

This is the first study to provide evidence that awakenings from NREM 2 sleep might underlie increased DRF in HFRs. This finding coupled with null findings in relation to REM sleep variables, support the premise that inter-individual variability in DRF cannot be ascribed to differences in REM sleep parameters in healthy individuals. Instead, the data indicates that awakenings from NREM sleep is of particular importance in relation to DRF in a healthy population.

Dream Recall and Content versus the Menstrual Cycle: A Cross-Sectional Study in Healthy Women

The association between sleep and the menstrual cycle has been scarcely studied. This study aimed to investigate the association between dream recall and content and the menstrual cycle among a large sample of young women. To this aim, 944 women were asked about their day of menstrual cycle, whether they remembered the previous night’s dreams and if they did so to describe the dream content as pleasant or unpleasant. A total of 378 women recalled the previous nights’ dreams, with 199 reporting pleasant dream affect/content and 179 reporting unpleasant dream content. In women who recalled their dreams, there was an association of pleasant dream content with the luteal phase (p = 0.038). In conclusion, in women, the hormonal milieu of the luteal phase may influence dream content.

Is dream recall underestimated by retrospective measures and enhanced by keeping a logbook? A review

There are two methods commonly used to measure dream recall in the home setting. The retrospective method involves asking participants to estimate their dream recall in response to a single question and the logbook method involves keeping a daily record of one's dream recall. Until recently, the implicit assumption has been that these measures are largely equivalent. However, this is challenged by the tendency for retrospective measures to yield significantly lower dream recall rates than logbooks. A common explanation for this is that retrospective measures underestimate dream recall. Another is that keeping a logbook enhances it. If retrospective measures underestimate dream recall and if logbooks enhance it they are both unlikely to reflect typical dream recall rates and may be confounded with variables associated with the underestimation and enhancement effects. To date, this issue has received insufficient attention. The present review addresses this gap in the literature.