Overview
This is mechanistic clinical trial that evaluates the role of one of the glutamate receptors (mGluR5) in cognitive behavioral therapy for insomnia (CBT-I) as a common pathway in improving sleep and depression.
Description
Cognitive behavioral therapy for insomnia (CBT-I), a treatment solely aimed at improving sleep, reduces depression with rates similar to conventional antidepressants. Although this efficacy reflects the interrelationship between sleep and depression, CBT-I's antidepressant mechanism of action is currently unknown. One potential mechanistic pathway is through the metabotropic glutamate receptor subtype 5 (mGluR5), due to its strong association with both depression and sleep. The investigators hypothesize that CBT-I's antidepressant efficacy may occur through the downregulation of mGluR5 associated with improved sleep. This study is a mechanistic clinical trial in a cohort of adults with MDD and a range of sleep latencies (time it takes to fall asleep). Prior to and following CBT-I, the investigators will quantify hippocampal mGluR5 density (with using positron emission tomography [PET] imaging) and sleep latency (with polysomnography performed in the Sleep Lab). CBT-I will be delivered through an online program, Sleep Healthy Using The Internet (SHUTi).
Eligibility
Inclusion Criteria:
- capacity to provide informed consent,
- at least 18 years of age
- good physical health and absence of significant medical conditions,
- diagnosis of major depressive disorder (MDD) with current major depressive episode as per DSM-5 criteria
- Montgomery-Åsberg Depression Rating Scale (MADRS) score > 29 (at least moderate depression),
- uniform range of sleep latencies up to 128 minutes.
Exclusion Criteria:
- currently taking effective antidepressants,
- lifetime history of psychosis,
- drug or alcohol dependence in the last 6 months or abuse in the last 2 months
- unstable medical condition (i.e., condition not adequately stabilized for ≥ 3 months)
- nicotine use within 1 year
- currently on medication known to affect glutamate,
- sleep disorders, other than insomnia, such as sleep apnea,
- recent (within 1 year) regular night shift work (or rotating shift work) or recent (within 3 months) travel across more than one time zone, or plans for this work or travel during the study period,
- use of medication or substances that affect sleep, for example, ingestion of more > 600 mg of caffeine per day,
- PET or MRI contraindications, including pregnancy or currently breastfeeding