In a nationally representative sample of adolescents, we found that sleep problems at a previous wave significantly predicted suicidality at a subsequent wave, while controlling for depression, alcohol-related problems, illicit drug use, and a number of demographic covariates. Specifically, W1 sleep problems predicted W2 suicidal thoughts and suicide attempts. Similarly, W2 sleep problems also predicted W3 suicide thoughts. However, W2 sleep problems had no direct effect on W3 suicide attempts. W1 sleep problems had both direct and indirect effects (via W2 depression) on W3 suicidal thoughts. Moreover, W1 sleep problems had an indirect effect (via W2 suicidal thoughts) on W3 suicidal attempts. To our knowledge, this is the first prospective study showing such a relationship in a nationally representative sample. Past longitudinal studies reported findings from relatively small samples or did not adequately control for important covariates such as depression and substance use.
Generally, the relationships between W1 predictors and W2 outcomes are stronger than the relationships between W2 predictors and W3 outcomes. For instance, no W2 predictors (other than W2 suicide thoughts) predicted W3 suicide attempts. This could be due to the longer time lapse between W2 and W3 than between W1 and W2. W1 and W2 is one year apart from one another, whereas W2 and W3 are five years apart. Nevertheless, in most of our analyses, sleep problems at a previous wave was either a direct or indirect predictor (via depression, suicide thoughts) of subsequent suicidal behavior. Moreover, sleep problems longitudinally predicted changes in alcohol-related problems, illicit drug use, and depression. Our results showed that W2 depression was the only significant mediator of the relationship between W1 sleep problems and W3 suicidal thoughts. However, as alcohol-related problems and illicit drug use are well known risk factors for suicidal behavior (Kessler et al., 1999
; Pena et al., 2012
), sleep problems may increase the risk of suicidal behavior via these two variables later in life (i.e., beyond W3).
Taken as a whole, results from this study and past research indicate that sleep problems is an important risk factor for suicidal thoughts and suicide attempts in adolescence. National data have indicated that sleep problems and sleep deprivation are prevalent among adolescents. In a recent national study, 51% of 6th–12th graders reported feeling tired or sleepy and 31% reported having difficulty staying asleep at night at least once in week in the last two weeks (National Sleep Foundation, 2006
). The active use of technology (e.g., computer with 24/7 internet access, cellular phone, video games) also have a significant impact on sleep in this age group. One study showed that among adolescents between the age of 13–18, 55% surfed the web every night or almost every night during the hour before going to bed and 56% sent or received text messages every night or almost every night before sleeping (National Sleep Foundation, 2011
). The same study also found that one in five adolescents was “sleepy” during the day and about one third (30%) said they drove while drowsy at least once in the past month.
Given the prevalence of sleep problems and sleep deprivation, prevention programs for adolescent suicide could include discussions of the importance of sleep, sleep hygiene, and the management of sleep problems and other sleep problems. The potential effect of technology use before bedtime on sleep and alertness is also an important topic of discussion. The frequent and habitual use of technology with “interactive” properties (e.g., computer use, video games, texting) may have both short- and long-term consequences on sleep and changes of circadian rhythms. The effectiveness of including sleep-related issues in adolescent suicide prevention programs is a topic for future research.
This study also has several clinical implications. The relationship between sleep disturbances and suicidal behavior underscores the importance of assessing sleep problems among adolescents who are at risk for suicide. An assessment of sleep disturbances should be included in the evaluation of suicidal risk, regardless of whether the adolescent has any prior history of psychiatric problems that may cause sleep problems. Adolescents may be more willing to discuss issues related to sleep than more sensitive topics such as depression and substance use. Sleep problems in these patients should be treated and such treatment may have a positive effect on the prevention of suicidal behavior. Future research could determine if early intervention with sleep disturbances reduces the risk for suicidality in adolescents.
The longitudinal relationship between sleep problems and suicidal behavior does not explain why this relationship exists. Recent research found that sleep problems may negatively affect mood and inhibitory processes, which may increase the risk of suicidal behavior. A meta-analytic study found that sleep deprivation had the greatest negative effect on mood, followed by cognitive tasks and motor tasks (Pilcher and Huffcutt, 1996
). Participants in one study reported less positive affect, experience more anxiety in a catastrophizing task, and rated the likelihood of potential catastrophes as higher when sleep deprived, compared to when rested (Talbot et al., 2010
). A fMRI study found that that a lack of sleep inappropriately modulates the brain response to emotionally aversive stimuli (Yoo et al., 2007
). Longitudinal studies have found that childhood sleep problems predicted depression and anxiety disorders in adolescence (Ong et al., 2006
) and adulthood (Gregory et al., 2005
). Thus, negative mood and depression may partially mediate the effects of sleep problems on suicidal behavior, which is consistent with past research on adolescent suicidality (Nrugham et al., 2008
) and the results of this study. More longitudinal research on the relationships among sleep problems, mood regulation, and suicidal behavior is necessary to understand how these variables reciprocally affect one another over time. A current review of studies on sleep problems and emotions indicate that they might have a bidirectional relationship – while heightened emotional arousal might contribute to the maintenance of sleep problems, dysfunction in the sleep–wake regulating neural circuitries might also reinforce emotional disturbances (Baglioni et al., 2010
Existing studies also indicate that sleep deprivation adversely affects inhibition or processes related to inhibition among adults (Chuah et al., 2006
; Harrison and Horne, 2000
; Tsai et al., 2005
). Among children, sleep deprivation negatively affected (Randazzo et al., 1998
) and sleep extension positively affected (Sadeh et al., 2003
) executive function tasks, i.e., tasks that require sustained attention and inhibitory processes. Finally, overtiredness in childhood predicted lower response inhibition in adolescence (Wong et al., 2010a
). Sleep problems may have a negative impact on inhibition and impulse control, which may increase the risk of suicidal behavior. Future research could examine how sleep problems and deprivation affect inhibitory processes and impulse control and whether such relationships increase the risk for suicidality among adolescents.
This study has several limitations. First, all measures were based on self-report which are subject to response and recall bias. No objective measures of sleep such as polysomnography or actigraphy were included. No information about individual sleep schedules or neurobiological parameters (e.g., structural and functional brain abnormalities) were analyzed in the study. Future studies need to include both subjective and objective assessment of sleep problems. Second, suicidal behavior and sleep problems were measured by single items. Although these items have face validity, the reliability of these measures is unknown. Future studies should use multiple items to measure these variables and estimate measurement error by doing latent variable analyses. Third, responses to the suicide items were recoded dichotomously. These items provided limited information on the underlying psychic states and psychological processes associated with suicidal thoughts and suicide attempts. Including other suicide items (e.g., severity of intent, frequency of attempts) could potentially reveal a more complex relationship between sleep problems and suicidal behavior. Fourth, other important predictors of adolescent suicidality (e.g., impulsivity, sexual abuse, physical abuse) were not included in the analyses. It was impossible to include these variables in the longitudinal analyses as they were measured only once. These variables should be included in future research. Fifth, a wide range of psychiatric disorders were not assessed. Most psychiatric disorders were associated with sleep difficulties or irregularities. The relationships between sleep problems and suicidal behavior reported in this paper could be due to the presence of psychiatric disorders (e.g., bipolar disorders, anxiety disorders). Future studies need to assess and statistically control for the presence of psychiatric disorders, especially those that are highly comorbid with sleep disorders and suicidal behavior.
In summary, among a nationally representative sample of adolescents, controlling for depression, alcohol problems, illicit drug use, and important covariates such as gender, age, and chronic health problems, sleep problems at a previous wave predicted suicidal thoughts (W2 and W3) as well as suicide attempts (W2) at a subsequent wave. Moreover, sleep problems longitudinally predicted depression, which significantly mediated the effect of sleep problems on suicidal thoughts.