The main finding of this study is that self-reported trouble sleeping between the ages of 12 and 14 was significantly associated with suicidal thoughts and self-harm/suicidal behaviors at ages 15–17, while adjusting for age, gender, prior suicidality, depressive symptoms, aggressive behavior, substance-related problems, COA status, and parental suicidal thoughts. This is to our knowledge the first prospective study of this relationship performed in the U.S. with a high-risk sample of adolescents.
Past research has found a strong association between depressive symptoms and suicidal behavior (Bettes and Walker, 1986
; Ivarsson et al., 1998
; Kovacs et al., 1993
; Nrugham et al., 2008
). However, a previous longitudinal study conducted in Norway failed to find a relationship between insomnia at age 15 and suicide attempts by age 20 after controlling for depressive symptoms (Nrugham et al., 2008
). As insomnia and other sleep disturbances are often associated with depression, it is important to examine whether sleep problems predict suicidal behavior after controlling for depressive symptoms. This study found that having trouble sleeping prospectively predicted suicidal ideation and self-harm/suicidal behavior, even after controlling for depressive symptoms. Our study and the Nrugham et al. (2008)
study differ in terms of sample characteristics (general students followed from ages 15 to 20 vs. high-risk community adolescents followed from ages 12 to 17; more girls vs. more boys); duration of follow-up (5 years vs. 3 years); instruments used to measure sleep, suicidality, and depression; and possibly culture. These differences might have explained the discrepancies in the results of the two studies. In any event, the present study draws attention to the potential importance of sleep problems as a marker for suicidal behavior in adolescence. Existing research also showed that sleep problems also prospectively predict depression (Gregory et al., 2005
; Gregory and O'Connor, 2002
), anxiety disorders (Gregory et al., 2005
; Gregory and O'Connor, 2002
), onset of substance use (Wong et al., 2004
; Wong et al., 2009
), and number of alcohol and drug related problems (Wong et al., 2010
). Thus sleep problems may be markers of a spectrum of risky behaviors, including suicidality.
Two other studies reported that nightmares (Choquet and Menke, 1990
) and tiredness (Choquet et al., 1993
) predicted suicidality in adolescents. Our study differs, however, by including all three sleep variables (insomnia, nightmares, and overtiredness) simultaneously in the multivariate analyses, which allows the variables to statistically control for one another. This is important as the three variables are correlated with one another in this study. Our results show that controlling for nightmares, overtiredness, depressive symptoms, and other variables in the study, having trouble sleeping at ages 12–14 significantly predicted suicidal behavior at ages 15–17. Future studies need to simultaneously assess the role of multiple sleep variables on suicidal behavior.
Contrary to our first two hypotheses, COAs were no more likely than non-COAs to report either sleep problems or suicidality as measured in this study. Adolescence is a time of both frequent sleep problems (Hagenauer et al., 2009
; Johnson et al., 2006
; Liu et al., 2008
) and increased suicidality (Cash and Bridge, 2009
). We can speculate, therefore, that a ceiling effect during this age period may exist for these problems that is unaffected by COA status.
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. Second, self-harm/suicidal behaviors were assessed by the single item, “deliberately try to harm or kill yourself.” Unfortunately, this compound item included both attempts to harm oneself and attempts to kill oneself, making it impossible to measure them separately. While trying to kill oneself is the definition of a suicide attempt, deliberate attempts to harm oneself may lack the intent to commit suicide. Therefore, this item more correctly refers to deliberate self-harm behavior that includes, but is not limited to, suicide attempts. Third, suicidal behavior and sleep variables were measured by single items. Although these items have face validity and have been used by other studies (Herba et al., 2008
; Johnson and Breslau, 2001
; Resch et al., 2008
), the reliability of these measures is unknown. The lack of an association between overtiredness, or having nightmares and subsequent suicidal ideation and self-harm behaviors could be in part, due to unknown measurement error. Future studies should use multiple items to measure these variables and estimate measurement error by doing latent variable analyses. Fourth, girls were underrepresented in this study, whereas Caucasians and COAs were overrepresented. Although gender and COA status were controlled for statistically, other ethnic/racial groups were not included; thus, results may not generalize to all adolescents.
Finally, a number of other predictors of adolescent suicidality were not included such as impulsivity and physical and/or sexual abuse (Cash and Bridge, 2009
). For instance, sexual abuse (Noll et al., 2006
) is associated with insomnia, and could potentially preclude the latter’s significance as a predictor of suicidality. Further studies employing larger sample sizes will need to control for these and other known risk factors. Nevertheless, from a clinical point of view, patients often feel more comfortable discussing sleep problems than either physical or sexual abuse. Therefore, sleep problems can be a useful marker for other risk factors during the interview process.
In summary, trouble sleeping was a predictor of both suicidal thoughts and self-harm/suicidal behavior in this longitudinal study of adolescents while controlling for baseline depressive symptoms and suicidality. To our knowledge, this is the first demonstration of such a relationship in a prospective study of adolescents. Of particular clinical interest, children were between the ages of 12 and 14 at the baseline interview, which preceded the well-established high-risk period for suicide in the general population of 15–24 year-olds. Moreover, trouble sleeping is relatively easy to assess in the clinical interview, and can begin a process of gentle questioning for other potential risk factors that may be less comfortable for adolescents to discuss. Accordingly, clinicians should inquire about sleep disturbances when assessing for suicidality in adolescents. Finally, future research should determine if early intervention with sleep disturbances reduces the risk for suicidality in adolescents.