Abstract
We sought to investigate the risk of incident major depressive disorder (MDD) attributable to a range of sleep disorders in the Danish population. Data were obtained by linking longitudinal Danish population-based registers. A total of 65,739 individuals who had first onset of depression between 1995 and 2013 were selected as cases. For each case, a set of 20 controls of the same sex, birth month and year and who had not had depression by the date that the case was diagnosed were selected at random form the population (N = 1,307,580 in total). We examined whether there was an increased rate of prior sleep disorders in MDD cases compared to controls using conditional logistic regression. An increased risk of incident depression in cases was found for all sleep disorders analyzed. Highest incidence rate ratios (IRRs) were found for circadian rhythm disorders (IRR = 7.06 [2.78-17.91]) and insomnia of inorganic origin (IRR = 6.76 [4.37-10.46]). The lowest estimated IRR was for narcolepsy (IRR = 2.00 [1.26-3.17]). Those diagnosed with a sleep disorder in the last 6 months were at highest risk of developing depression compared to those with at least 1 year since diagnosis (3.10 vs. 2.36). Our results suggest that having any sleep disorder is a risk factor for incident depression. Depression screening should be considered for patients with sleep disorders, and where possible, long-term follow-up for mental health problems is advisable.
Highlights
Difficulties with sleep and disruptions to circadian rhythms are hallmarks of psychiatric disorders
For disorders for which there were sufficient number of cases to separate into categories according to how recently relative to the onset of depression the sleep disorder was treated, we evaluated the incidence rate ratios (IRRs) according to time since onset
We found that obstructive sleep apnea (OSA) is a stronger risk factor for depression than other types of Sleep-Disordered Breathing (SDB)
Summary
Difficulties with sleep and disruptions to circadian rhythms are hallmarks of psychiatric disorders. In the case of mood disorders, disruptions to sleep can form part of a clinical diagnosis based on the criteria established in the Diagnostic and Statistical Manual of Mental Disorders (5th ed., DMS-V, American Psychiatric Association, 2013). Both insomnia and hypersomnia can form part of a diagnosis of major depressive disorder (MDD), the most common mood disorder (Pedersen et al, 2014). An important aspect of treating sleep disorders is understanding the risks of developing MDD in patients and ensuring that appropriate For some disorders such as parasomnias and circadian rhythm disorders, studies showing increased rates of depression in cases have only been correlational or cross-sectional, since longitudinal studies are costly. We utilize the Danish national registers, which contain records on all general and psychiatric hospital visits for the entire Danish population
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