Hypersomnia in Major Depressive Disorder
Hypersomnia in Major Depressive Disorder
Background: MDD is a common mental disorder with significant morbidities and mortalities.
 Recent local data suggested that depressive disorders have a prevalence of over 12% in
 females and nearly 7 % in males in Hong Kong general adult population. Other than insomnia,
 patients with MDD often complained another sleep symptom - hypersomnia (defined as daytime
 sleepiness or excessive sleep). Interestingly, when compared to insomnia, there is much far
 less research on the role of hypersomnia in MDD. However, there are available data suggested
 that hypersomnia is associated with greater treatment-resistance, more recurrence, and
 increased suicidality, suggesting a need to investigate this problem in MDD patients.

 Objective: To investigate the prevalence and determine characteristics of hypersomnia amongst
 major depressive disorder.

 Design: 2-phase study design Setting: A case-control study Participants: Patients with a
 history of Major Depressive Disorder from out-patient clinics in New Territories East
 Cluster.

 Main outcome measures: Daytime sleepiness measured by MSLT, actigraphy and self-reported
 questionnaire (ESS), sleep duration as measured by sleep diary and actigraphy.
Background

 Significance of hypersomnia in depressive illness

 Sleep disturbances are observed in up to 90% of depressed patients. Both insomnia, defined
 clinically as difficulty initiating and/or maintain sleep, and hypersomnia, defined as
 excessive daytime sleepiness (EDS) and/or excessive sleep duration, are key symptoms in the
 diagnostic criteria of depression. A sizeable number of studies have demonstrated clear
 associations between insomnia and poorer depressive outcomes. These include greater
 depressive symptom severity, poorer treatment response and increased risk of suicidal
 ideations and attempts. Persistent insomnia complaints following remission of major
 depressive episodes (MDE) have also been found to be associated with greater risk of
 recurrence, poorer overall functioning and quality of life. Compared to insomnia, there is
 much less research on the role of hypersomnia in depressive illness.

 Studies so far have suggested a prognostic significance. Hypersomnia in depressed subjects
 amongst a mix of mood disorders have been linked to greater treatment-resistance, depressive
 relapse, higher suicidal ideations and increased risk of suicide; while hypersomnia
 complaints amongst general populations have predicted the risk of incident depression. More
 recently, studies of depressed individuals amongst a mix of mood disorders had further found
 that the concurrence of insomnia and hypersomnia was associated with worse symptomatology
 compared to patients with insomnia or hypersomnia alone. These studies also found that the
 concurrence of insomnia and hypersomnia had greater associations with bipolar spectrum
 features, which builds on from previous findings suggesting that hypersomnia itself may be a
 clinical marker for undetected or subsequent diagnosis of bipolar II disorders in depressed
 patients.

 Knowledge gaps in the understanding of hypersomnia in major depression

 Despite its prognostic implications, there is currently a lack of studies investigating
 potential determinants or clinical correlates of hypersomnia in major depressive disorder
 (MDD). MDD is one of the commonest diagnoses encountered in the outpatient setting, and may
 be distinct in its determinants and outcomes compared to other mood disorders. Existing
 studies on hypersomnia in depression have predominantly included subjects from a mix of mood
 disorders; thus, a gap exists to extend the scope of understanding on hypersomnia amongst
 unipolar depression.

 Due to the lack of standardized definitions, even amongst contemporary classifications, there
 is little clarity as to which aspect of hypersomnia - i.e. whether EDS or excessive sleep
 duration, or in combination - is related to poorer depressive outcomes. Moreover, little is
 known about what severity of "excessive" daytime sleepiness and sleep duration may be of
 clinical significance. Most studies of hypersomnia in mood disorders have used crude
 definitions, predominantly in form of single yes/no questions, to define hypersomnia. Despite
 the availability of validated questionnaires such as the Epworth Sleepiness Scale (ESS) that
 could help quantify EDS, or the use of sleep diaries that may help determine an individual's
 average sleep duration, limited studies of hypersomnia in MDD have employed these tools. The
 variability in definitions have also resulted in a large range of reported prevalence -
 between 8.9% to 78% of hypersomnia in MDD samples. In order to generate more clinically
 useful data, it may be helpful to "deconstruct" hypersomnia into EDS and prolonged sleep
 duration, to quantify them using validated or clinically-relevant measures, and further
 analyze their associations with potential determinants and depressive outcomes.

 Theoretically, a myriad of factors can contribute to EDS or prolonged sleep duration. These
 include physical-health related factors, such as the use of sedative medications, the
 presence of medical illnesses and sleep-related breathing disorders; also sleep-related
 factors, such as the need for shift-work, the presence of insomnia or other sleep-behavioral
 disturbances, or the presence of circadian-disorders or particular chronotype preferences.
 Psychiatric factors, such as increased anxiety, somatic complaints and perceived fatigue
 levels, may also be related to EDS or prolonged sleep duration. So far, no studies have
 simultaneously examined this range of factors and their potential associations with
 hypersomnia complaints in MDD. Whether these factors mediate or act synergistically with
 hypersomnia to influence depressive outcomes remain to be elucidated.

 A limitation that many hypersomnia studies have faced is the lack of objective measures used
 to corroborate subjective measures of EDS or sleep duration. The mean sleep latency test
 (MSLT) is currently regarded as the gold standard objective measure for EDS, while
 polysomnography (PSG) and wrist actigraphy has been useful in validating sleep diary data.
 However, the costs, expertise and time required to conduct these tests have limited their
 use. A study involving the use of both subjective and objective measures of EDS or sleep
 duration, in addition to a thorough analysis of the potential determinants and clinical
 correlates, may provide valuable information on the clinical profiles of hypersomnia patients
 and shed light on areas for further research and management.
Inclusion Criteria:

 -  patients aged between 18-64 years old with a history of MDD

 Exclusion Criteria:

 -  patients with history of bipolar disorder, schizophrenic-spectrum disorder, substance
 abuse, alcohol dependence, dementia, patients with history of mental retardation and
 those unable to give consent.