Is Insomnia a Predictor of Mental Illness?

A quote attributed to Benjamin Franklin is “An ounce of prevention is worth a pound of cure.” With that in mind, the field of psychiatry continues to aim to identify early indications of mental illness to initiate early treatment, since expedient treatment has been shown to positively affect the outcomes of many psychiatric disorders. Indeed, there is an unmet need for preventive strategies that delay or forestall the onset of mental illness, particularly in persons at heightened risk. Consequently, researchers have looked at insomnia—a syndrome with chronic problems related to sleep onset and/or continuity that are associated with impaired daytime functioning—as a potential predictor of new-onset major depressive disorder in 2 meta-analyses with odds ratios (ORs) of 2.3 to 2.6.^1,2

Hertenstein and colleagues³ performed a systematic, quantitative review of longitudinal studies, investigating whether baseline insomnia (including both nighttime and daytime symptoms) is associated with subsequent onset of a mental disorder. Study authors searched for articles in PubMed, Medline, PsycInfo, and PsycArticles, as well as the reference lists of identified studies and recent congress abstracts.

Longitudinal studies were included if they met the following criteria: follow-up lasted at least 12 months for adults in whom insomnia was diagnosed, based on interview or questionnaire (and covering both nighttime and daytime symptoms); diagnoses of mental disorders were verified by clinical interview or validated self-rating questionnaires; and either participants with mental disorders other than insomnia at baseline were excluded, or the study controlled for baseline psychopathology. Data were analyzed using random effects meta-analysis. Effect sizes (ORs) were calculated for individual mental disorders as well as all mental disorders pooled together. The authors performed assessments of both risk of bias and publication bias.

The authors identified 13 studies, comprising a total sample of 181,798 participants at baseline and 133,967 at the last follow-up. These studies included 10 samples for depression, 6 for anxiety, 2 for alcohol abuse, and 1 for psychotic disorders. The mean duration of study follow-up was 61 months. They found that baseline insomnia was associated with significantly increased odds of incident depression (OR, 2.8), anxiety (OR, 3.2), alcohol abuse (OR, 1.4), and psychosis (OR, 1.3).

Across all studies pooled together, baseline insomnia was associated with a significant, 2.6-fold increased odds of mental disorder, with evidence of significant between-study heterogeneity. Overall, the risk of bias was rated as moderate for most individual studies. There was no significant evidence of publication bias for either depression or anxiety. There was no evidence that study duration moderated these associations. Furthermore, the pattern of findings did not change in a subgroup analysis of studies of participants without any mental disorders at baseline.

The authors concluded that baseline insomnia is associated with significantly increased odds of incident mental disorder. Potential explanations for these associations include brain hyperarousal, neuroplasticity, and emotion regulation. A strength of the meta-analysis is that both nighttime and daytime symptoms of insomnia were required for inclusion, consistent with current diagnostic criteria. The authors noted, however, that the observed temporal association does not allow for causal attributions. Nevertheless, findings raise the possibility for treatment of insomnia for the prevention of mental disorders.

Dr Miller is a professor in the Department of Psychiatry and Health Behavior, Augusta University, Augusta, Georgia. He is the schizophrenia section chief for Psychiatric Times™. The author reports that he receives research support from Augusta University, the National Institute of Mental Health, the Brain and Behavior Research Foundation, and the Stanley Medical Research Institute.

References

1. Baglioni C, Battagliese G, Feige B, et al. Insomnia as a predictor of depression: a meta-analytic evaluation of longitudinal epidemiological studies.
J Affect Disord. 2011;135(1-3):10-19.

2. Li L, Wu C, Gan Y, et al. Insomnia and the risk of depression: a meta-analysis of prospective cohort studies. BMC Psychiatr. 2016;16(1):375.

3. Hertenstein E, Feige B, Gmeiner T, et al. Insomnia as a predictor of mental disorders: a systematic review and meta-analysis. Sleep Med Rev. 2019;43:96-105.