Introduction
Psychotic-like experiences (PLEs) capture a range of subclinical phenomena that cannot be the basis for diagnosing mental disorders due to insufficient severity or impact on general functioning. The lifetime prevalence of PLEs has been estimated at 5.8% of the general population; however, it might be higher in younger people [
1,
2]. It has been shown that PLEs do not form a discrete categorical construct but are distributed dimensionally in non-clinical populations and high-risk individuals [
3,
4]. Notably, PLEs are not the predictors specific for the development of psychosis, but are associated with a variety of mental health outcomes [
5]. Therefore, investigating PLEs, as substrates of subclinical psychopathology, might be informative for interventions targeting preclinical stages of mental disorders.
It is important to note that PLEs cover a range of delusion-like and hallucination-like phenomena that are known to predict the development of various mental disorders that fall beyond the psychosis spectrum [
5‐
7]. Factor analyses of tools that record the presence of PLEs also show that they do not form a homogenous construct [
8]. In this regard, the approach based on the assumption that a common latent disorder or mechanism underlies the development and consequences of PLEs might be insufficient. A novel approach, i.e., the network analysis assumes that psychopathology covers the systems of causally associated symptoms rather than the effects of a latent disorder or mechanism [
9‐
11]. The network analysis has already been applied by studies that aimed to understand the phenomenology of PLEs and their associations with risk and protective factors as well as other domains of psychopathology. For instance, it has been found that PLEs are associated with a variety of social and behavioral problems, suicidal behavior, and depressive symptoms in adolescents [
12]. Another study demonstrated the importance of social contexts in understanding the consequences of PLEs [
13]. The authors of this study found that PLEs are significantly less interconnected and show weaker associations with the level of distress in populations representing low- and middle-income countries compared to those from high-income countries.
Although PLEs are subclinical phenomena, it has been shown that these experiences are significantly associated with the risk of suicidal thoughts, plans and attempts [
14‐
16]. However, specific PLEs might be differentially associated with a risk of suicidal ideation and behaviors with particularly strong associations reported for thought control, auditory hallucinations, suspiciousness, and nihilistic thinking/dissociative experiences [
17]. Moreover, little is known about processes that moderate the association between PLEs and suicide risk. For instance, it has been found that greater impulsivity and emotion dysregulation make individuals with PLEs more prone to develop suicidal ideation and behaviors [
18].
There is accumulating evidence that PLEs are associated with poor sleep quality [
19‐
21]. Studies based on longitudinal designs and experience sampling methodology suggest that there might be a bidirectional association between poor sleep quality and PLEs [
19,
22,
23]. It has also been demonstrated that cognitive-behavioral therapy of insomnia might reduce the level of paranoia and hallucinations in university students [
24]. Moreover, experimental studies show that sleep deprivation initiates the onset of PLEs, and that PLEs are reduced after restoring sleep schedules [
25,
26]. Taken together, these observations suggest a vicious cycle conceptualization in which sleep disturbance gives rise to PLEs that might in turn contribute to increased distress further enhancing poor sleep quality [
27]. Importantly, there is evidence that sleep disturbance and PLEs might share overlapping neural mechanisms represented by a reduction in volumes of the left thalamus as recently reported [
28].
As similar to PLEs, sleep disturbance might be associated with increased risk of suicide. For instance, a recent meta-analysis of cohort studies revealed that sleep disturbance is associated with over threefold higher incident risk of suicide attempt and almost twofold higher incident risk of completed suicide [
29]. Another meta-analysis of sleep measures demonstrated that decreased total sleep time is related to current suicidal behaviors [
30]. However, little is known about the interaction between sleep disturbance and PLEs in impacting suicide risk. To date, only one study tested this effect in help-seeking individuals [
31]. The authors observed that PLEs are associated with suicidal ideation only at higher levels of sleep difficulties. Nevertheless, this study did not investigate which specific PLEs contribute to suicidal ideation at higher levels of sleep disturbance. In this regard, we aimed to extend these findings over a larger sample of non-clinical young adults. Specifically, the aim of our study was to test the moderating effect of insomnia on the association between PLEs and the current suicidal ideation. Additionally, we explored which PLEs are related to the current suicidal ideation at various levels of insomnia in the network analysis.
Discussion
Findings from our study indicate that PLEs are associated with the current suicide risk only in subjects with insomnia after controlling for the effects of sociodemographic characteristics and depressive symptoms. These findings are in agreement with those obtained by Thompson et al. [
31], who also found a moderating effect of sleep quality on the association between PLEs and suicidal ideation in help-seeking individuals. Our findings extend these observations over the non-clinical sample of individuals with less severe psychopathological symptoms. Moreover, a recent study performed in college students demonstrated that previous suicidal ideation and low subjective quality of sleep are the most robust predictors of the current suicidal ideation [
51]. Other factors associated with higher risk of the current suicidal ideation in this sample included paranoid thoughts, internet addiction, poor self-rated physical health, poor self-rated overall health, emotional abuse, low average annual household income per person and heavy study pressure.
Another important observation from this study is that deja vu experiences, auditory hallucination-like experiences and paranoia might be most closely related to suicidal ideation in subjects with PLEs reporting insomnia. No connections between nodes of PLEs and the node of current suicidal ideation were found in participants without insomnia. Further, nodes representing paranoia and deja vu experiences represented the three most central nodes in the network analysis of participants with insomnia. Also, the item that captured paranoia (“conspiracy about me”) had the highest predictability in participants with insomnia. In turn, depressive symptoms were the three most central nodes in the network analysis of participants without insomnia. The PHQ-9 item 6 (“feeling bad about yourself”) had the highest predictability in this subgroup of participants. The connection between deja vu experiences and the current suicidal ideation had the largest edge weight among connections between PLEs and the current suicidal ideation. The phenomenological position of deja vu experiences remains unclear. However, some authors classify deja vu experiences among dissociation symptoms [
52]. It has been found that dissociation might be a transdiagnostic risk factor of suicide [
53]. In general, our findings are also similar to those obtained by Jay et al. [
17], who demonstrated that thought control, auditory hallucinations, suspiciousness, and nihilistic thinking/dissociative experiences represent PLEs that are the most strongly associated with suicidal ideation among children with PLEs. Moreover, paranoia has been repeatedly associated with higher risk of suicide in clinical and non-clinical samples [
54‐
56].
Our findings should be interpreted with caution due to certain limitations. We did not use any standardized tools to assess psychiatric diagnosis in participants. Therefore, translation of findings into clinical practice should be approached cautiously. However, there is evidence that PLEs represent a transdiagnostic risk factor of mental disorders [
6,
7]. Moreover, self-reported PLEs have been found to predict the development of psychosis in epidemiological studies of non-help-seeking individuals [
57]. Also, self-reported PLEs that have been found to represent false positive findings in standardized clinical assessment might predict the development of psychosis, mood and anxiety disorders as well as low social functioning [
58,
59]. Another limitation is that the use of a snowball sampling methodology might be characterized by limited accuracy and low representativeness of participants [
60]. Indeed, we were not able to record the number and data of participants who declined to participate in the survey. Moreover, causal associations cannot be indicated as the cross-sectional design was used. However, according to existing evidence in the field, bidirectional associations between PLEs and sleep disturbance are most likely to occur [
19,
22,
23]. Also, all assessments were performed using self-reports with selected items derived from specific tools. Among them, suicidal ideation was assessed using only one item from the PHQ-9 (item 9). This item might also capture the current intent of non-suicidal self-injuries and does not cover all aspects of suicidality (e.g. lifetime occurrence of suicide attempts, ideations and plans). However, in the present study, we focused on the current psychopathology. Also, it has been shown that the PHQ-9 item 9 might hold usefulness in stratifying the risk of suicide [
61‐
63]. At this point, it is also important to highlight the lack of objective measures for insomnia. Finally, it needs to be pointed out that results of the network analysis might depend on the inclusion of specific variables. In this regard, it should be noted that the association between PLEs and the current suicidal ideation reported in the present study might simply reflect shared correlates of PLEs and suicidality (e.g. childhood trauma, substance use, and other dimensions of psychopathology) [
64].
In sum, observations from the present study provide certain translational perspectives that might be of importance in clinical practice. Specifically, our findings indicate that insomnia might be an important aspect in subjects with PLEs increasing the occurrence of suicidal ideation. From the phenomenological point of view, deja vu experiences, hallucination-like experiences and paranoia might be more closely related to suicidal ideation in subjects with PLEs who also report insomnia. Targeting sleep quality might be important for suicide prevention among individuals with PLEs. However, additional studies in clinical samples are needed to develop specific recommendations.