1. Introduction
Parasomnias are a group of sleep disorders characterized by abnormal and unpleasant motor, verbal, or behavioral events that occur during sleep or wake to sleep transitions [
1]. They can be quite distressing for the individual experiencing them and are often very disturbing for a bed partner.
1.1. REM and NREM Parasomnias
During sleep, the brain cycles regularly between wakefulness and two sleep phases (nonrapid eye movement (NREM) and rapid eye movement (REM)). The classification of most parasomnias depends on whether they have emerged from NREM or REM sleep [
2]. The following three tables show examples of the most common of these [
3].
NREM parasomnias involve physical and verbal activity of varying complexity. Typically, the sleeper returns to sleep and is amnesic in the morning (behavior is reported by others, discovered because items have been moved or used during the night, or the events have resulted in injury). During NREM parasomnias people’s eyes tend to be open. NREM parasomnias occur most frequently in the first third of the night (see
Table 1).
In contrast, characteristics of REM parasomnias include verbalizations and actions consistent with dream enactment. These parasomnias often include fight or flight behaviors that usually awaken the sleeper who, unlike those with NREM parasomnias, can often recall the event, the dream, and the associated actions. During REM parasomnias people’s eyes tend to be closed. REM parasomnias occur most often in the last third of the night (see
Table 2).
Other parasomnias, including exploding head syndrome, sleep enuresis (bed wetting), and sleep-related suffocating, are not specific to either NREM or REM sleep phase and may occur at any point during the sleep cycle (see
Table 3).
Notably, the most frequently used parasomnia questionnaire—the Munich Parasomnia Screening Questionnaire (MUPS) [
4]—includes several items that occur at night and may disrupt sleep, which are classified by the ICSD-3 [
3,
5] as movement disorders, such as periodic twitching and kicking while asleep, nocturnal leg cramps, and sleep-related bruxism. In addition, the MUPS also contains items that do not emerge from a specific sleep stage, but rather are more accurately defined as phenomena occurring during the transition from wake to sleep at the beginning of the night, sleep to wake at the end of the night, or from one sleep stage to another. Examples of such “transition phenomena” are hypnagogic (while falling asleep) and hypnopompic (while waking up) hallucinations, and hypnic jerks and rhythmic leg movement, which occur at the transition from quiet wakefulness to sleep. As Stieglitz and Heppner [
6] noted, “Nocturnal phenomena, such as teeth grinding (bruxism), nocturnal cramps, repeated twitching of the legs or kicking, REM sleep-associated cardiac arrest or REM sleep-associated AV nodal block, as well as chocking and suffocating during sleep, are no longer classified by name in the current ICSD-3. But these other parasomnias may be found in sleep self-rating tools, such as the Munich parasomnia screening (MUPS)”.
1.2. Causes and Consequences
Generally, triggers and exacerbating factors for parasomnias include sleep deprivation, delayed sleep phase disorder, insomnia, and anxiety [
7]. External events such as noise and temperature change, or internal events such as sleep apnea, restless leg syndrome, and periodic limb movement disorder, may cause an arousal or partial awakening, usually from NREM Stage N3 sleep [
8]. These occur in the first 90 minutes of the sleep period. Arousal or partial awakening can also occur during NREM stages N1 or N2 sleep later in the night. Shift work may also increase risk for REM and non-REM parasomnias [
9].
These negative sleep-related phenomena can have detrimental impacts, such as sleep-related injuries (e.g., from sleepwalking and REM behavior disorder), daytime sleepiness (e.g., sleep deprivation), and psychological distress (e.g., nightmare disorder, sleep-related hallucinations, sleep paralysis). For example, Kelly [
10] found that, in a sample of 373 American undergraduates, individuals who reported frequent nightmares also reported higher levels of depression, anxiety, and neuroticism. In addition, Alshahrani et al. [
11] also found that parasomnias among university students were significantly associated with depression and anxiety, corroborating research on the well-established links between parasomnias and mental health issues [
9].
1.3. Prevalence
Past research on parasomnias predominantly focused on children [
7], who typically “outgrow” these, and on clinical populations [
12]. Studies targeting college students have been limited until recently.
Indeed, we have been able to find only four studies where the focus was on college students or young adults. An early study [
13] in Nigeria found that over 70% of university students reported experiencing at least one parasomnia at some point in the past, with nightmares, enuresis, sleep paralysis and night terrors being the most common. A more recent study by Kirwan and Fortune [
14] in Ireland investigated the one-year prevalence rates of parasomnias among 135 university students. This study showed that nearly all participants (98%) had experienced at least one parasomnia during the past year, with over a quarter (28%) reporting seven or more. Hypnic jerks, nightmares, and sleep-talking were the most prevalent. Similarly, Alshahrani et al. [
11] in Saudi Arabia studied a large university sample of 1296 students and found that 81% reported at least one parasomnia. The most prevalent during the previous six months were sleep-talking (51%), nightmare disorder (50%), and confusional arousals (40%). They also reported that parasomnias among university students were significantly associated with psychological stress, depression, and anxiety disorders. In a study on young adults [
10], Matsui et al. found that 2.2% of their participants experienced sleep-related eating disorder-like behavior. This parasomnia was associated with smoking, the use of hypnotic medication, and previous and/or current sleepwalking.
Although these studies show that parasomnias, especially nightmares, are common among college students, there are a variety of minor differences in prevalence among the findings. These may stem from a range of factors, such as cultural, national, or regional differences, variations in the measures, and discrepancies in the timeframe (e.g., over the past fourteen days, past six months, past year, or lifetime). Notably, there are no data on the one-year prevalence of parasomnias among post-secondary students in North American countries, including Canada.
None of these investigations explored how distressing the parasomnias were to students nor how students dealt with these. In addition, there has been no systematic investigation of co-occurrence of the parasomnias in the same individual.
1.4. Present Study
The goals of this study were to (1) explore the one-year prevalence of the 21 parasomnias listed on the most frequently used, validated parasomnia measure in a population of current and recent post-secondary students, (2) evaluate whether an individual with one specific parasomnia will have another specific parasomnia, (3) assess how disturbing each parasomnia was to current and recent students, and (4) explore what they did to cope with the parasomnia.
We hypothesized that, as in other studies:
- (1)
Over 70% of students would report at least one parasomnia during the past year;
- (2)
Most students would report two or more types of parasomnias;
- (3)
Nightmare disorder would be the most prevalent parasomnia reported.
In addition, the following hitherto uninvestigated areas were explored. These additional analyses add new, interesting, and useful insights:
- (4)
Investigating students’ distress levels related to specific parasomnias;
- (5)
Identifying their coping strategies for each parasomnia;
- (6)
Exploring the co-occurrence of different parasomnias in this population.
4. Discussion
Our findings in this under-researched population show that the one-year prevalence of parasomnias among North American college students and young adults is very high and that many of these parasomnias are disturbing and distressing, with nightmares being especially common. This is true even though our sample was primarily healthy since we excluded those who self-reported a disability, including mental health problems (cf. [
11]). In this mainly healthy sample, we found the number of students who experienced parasomnia and negative sleep experiences at least once during the past year to be extraordinary. Moreover, our findings show that when a student has a parasomnia, they are likely to have other parasomnias as well; very few students have just one.
As predicted in Hypothesis 1, 92% of our sample had at least one parasomnia. This was consistent with the results of Kirwan and Fortune [
14], who reported that 98% of their sample experienced one or more recent or current parasomnias. As predicted in Hypothesis 2, most (77%) participants had at least three. Having only one parasomnia was rare. As predicted in Hypothesis 3, nightmares were particularly common, with 82% of participants reporting that they had experienced these during the past year. This was also true in the three other studies investigating parasomnias in college students [
11,
13,
14]. In the present sample, parasomnias experienced were generated from all stages and phases of sleep, including transitions between wake and sleep states.
In general, sleep deprivation, delayed sleep phase disorder, insomnia, and anxiety [
7], noise and temperature change, as well as conditions such as sleep apnea, restless leg syndrome, and periodic limb movement disorder can have detrimental impacts and cause a variety of parasomnias [
8].
4.1. Relative Co-Occurrence
We wanted to learn which parasomnias exist together. Our findings indicate that nightmares and sleep talking have the greatest overlap with other parasomnias. Others seem to overlap minimally (e.g., exploding head syndrome, sleep terrors). Knowing how likely parasomnias co-occur demonstrates that REM and NREM parasomnias did not appear to follow any predictable or expected principle.
The results show that participants who had nightmares (a REM parasomnia) were also likely to have the following NREM parasomnias (hypnic jerks and sleep talking), as well as parasomnias that can occur in either REM or NREM stages, such as nocturnal leg cramps and sleep-related bruxism. Those who experienced sleep talking (an NREM parasomnia) were also likely to have nightmares (a REM parasomnia), as well as hypnic jerks and periodic twitching and kicking while asleep (NREM parasomnias). Many other parasomnias were also associated with each other.
4.2. Parasomnia Frequency, Disturbance and Distress Aspects
Our research examined not only the prevalence, but also the one-year frequency and the degree of disturbance of parasomnias. Eliciting subjective perceptions about how disturbing the phenomenon is merits attention, since the parasomnia that causes the most distress for an individual is not necessarily the most frequently experienced one. The most common prevalence of parasomnias, in rank order, were nightmares, hypnic jerks, sleep talking, sleep-related bruxism, nocturnal leg cramps, rhythmic leg movements while falling asleep, and periodic twitching and kicking while asleep.
Our findings also show that although few participants reported nocturnal leg cramps and hypnagogic/hypnopompic hallucinations, these occurred more often than other parasomnias. Both these parasomnias were perceived as moderately disturbing. In addition, while many participants experienced nightmares as well as sleep related bruxism, these were generally not experienced frequently. However, for the many individuals who did experience them, these parasomnias were quite disturbing. When we examined only those parasomnias that participants indicated occurred often, nocturnal leg cramps, sleep enuresis, sleep paralysis, nightmares, and nocturnal eating were the most disturbing.
There were several other disturbing parasomnias, but these were experienced by few participants or were experienced infrequently. With few exceptions, disturbing parasomnias tended to occur during NREM and in those which involved physical movements. In rank order these are sleep enuresis, sleep paralysis, sleep terrors, sleep-related abnormal choking/suffocating, nocturnal leg cramps, nightmares, and exploding head syndrome.
It is important to note that some of the parasomnias are unique to age groups. For example, sleep enuresis is common among children [
18] and REM sleep behavior disorder is more common among older adults [
19], not among the young adults in our sample.
4.3. How Do Students Cope with Disturbing/Distressing Parasomnias?
It is important to note that the most common way that students managed their parasomnia, be it frequent or infrequent and be it very or mildly disturbing, was to do nothing about it. This was especially true of hypnic jerks, nightmares, nocturnal leg cramps, and sleep related bruxism. Even for disturbing parasomnias, such as sleep related groaning, students reported that they did nothing to cope with it, suggesting that they did not know what to do. It is worth mentioning that students did not report that they turned to self-medication with drugs or alcohol.
The largest number of students who indicated a means of trying to manage their parasomnia used a grounding strategy (e.g., taking actions to relax and calm oneself down). Participants implemented grounding for many parasomnias, including nightmares, exploding head syndrome, hypnagogic hallucinations, and confusional arousals, among others. It is important to note that many of those reporting nightmares also reported using distraction strategies such as scrolling on their smartphones or texting with friends.
The second most frequently mentioned coping strategy was prevention. Students were especially likely to use these strategies for nightmares (e.g., changing what they chose to watch or listen to before bed, changing their bedtime) and tooth grinding (e.g., using jaw exercises or mouth guards). Students tended to use physical manipulation of their body for physical parasomnias such as nocturnal leg cramps, rhythmic movement disorder, and sleep related abnormal choking suffocating.
4.4. Developmental and Age-Related Considerations
Notably, some parasomnias are more characteristic in different age groups. For example, sleep enuresis is relatively common among children [
18,
20], but very infrequent in adults; REM sleep behavior disorder usually only begins in the fifth or sixth decade of life [
19,
20], suggesting a developmental component in this sleep-related experience. Our own study, by its unique focus on parasomnias and other sleep disturbances in the late adolescence and early adulthood college student cohort, adds a hitherto unexplored piece to general knowledge. It is known that the various parasomnias follow somewhat predictable patterns across the lifespan. The present data appear to reinforce the existence of a transitional developmental trajectory between childhood and later adulthood, which includes parasomnias and other sleep disturbances most associated with these life stages.
It has been noted that many parasomnias, particularly those associated with NREM sleep, have the highest prevalence in children, tend to decrease in frequency after the onset of puberty, and become rare in adulthood. This pattern suggests a developmental and maturational trajectory of the nervous system (e.g., night terrors) as well as the development of self-regulation of body functions, even while asleep (e.g., enuresis) [
21].
Nevertheless, sleep terrors were reported by a surprising number of participants (17%) overall, while 6.5% rated them as very frequent and disturbing. Night terrors have a prevalence of 37% to 20% during early childhood, and a prevalence of 2.2% in the general adult population [
22].
The experience of occasional nightmares is very common in the general adult population, ranging from 22% to 45% [
23], and in children, ranging from 60% to 75% [
7]. Nightmare disorder, the diagnosis of which is made largely by self-report, occurs in about 5% of children [
22] and in about 4% of the general adult population [
24]. In the present young adult sample, 82% reported the occurrence of nightmares in the past year, and 6.5% rated both the frequency and disturbance level as high. It is important to take into account the unique pressures experienced by young adults as they advance through their education and assume careers and other responsibilities.
5. Limitations
There are issues related to the generalizability of the findings. The frequency of occurrence of these negative sleep events appears, in general, very high for a young, relatively healthy sample. This may in part be due to the fact that they are self-reported compared to some research estimates that are based on diagnostic interviews or objective measurements such as polysomnography. Some parasomnias such as sleep terrors and REM sleep behavior disorder may be under-reported by our sample because these need corroboration from someone sleeping in proximity to the student. Furthermore, we excluded students with mental health related disabilities, even though we expected that students with various disabilities would have higher rates of parasomnias. Research on students with disabilities and parasomnias, as well as on other risk factors and resilience, are ongoing in our laboratory. In addition, it was not possible to calculate power for basic frequency and coding data and the sample size of 77 is relatively small. Also, there were few participants who indicated a non-binary gender (e.g., transgender, gay, lesbian, agender), and most participants studied in only one of Canada’s ten provinces.
6. Conclusions and Implications
Our study brings new insights into clinical monitoring by highlighting the extensive prevalence and co-occurrence of specific parasomnias among current and recent students. Our findings clearly show that although 92% of students experience an assortment of parasomnias, with a large variety of frequency and levels of disturbance, they know little about effective means of managing these. In particular, raising awareness of nightmares as an important health concern is critical. In a study of 747 undergraduate students, only 11% of participants with significant nightmares reported having told a healthcare provider about their nightmares [
25].
Moreover, in our team’s sleep clinic, those presenting with sleep problems rarely mention parasomnias. The same experience is true of general practitioners and medical sleep specialists, as our Advisory Board members indicated [
26]. Our study highlights the need for comprehensive sleep assessments and targeted interventions. Clearly it is important to have an idea about techniques to address the most disturbing and the most frequent parasomnias. Regrettably, there are very few “tried and true” validated means of dealing with these (see current suggestions for the most common or distressing parasomnias in
Appendix B).
A more salient point is how to communicate potential strategies to those individuals who experience high levels of disturbance, especially to students and other young adults. They do not appear to seek professional help, as many prefer peer advice, nor are they likely to read professional journals. The answer appears to lie in social media platforms such as Redditt, TikTok and Instagram. Perhaps these will become the new vehicles of dissemination of research-based strategies to diminish the occurrence of disturbing parasomnias in postsecondary students.