The study population comprises three groups of 30 analyzable participants: Patients with sleep inertia and Major Depressive Disorder, patients with Major Depressive Disorder but without sleep inertia, and controls without mood disorders or sleep inertia. Controls will be patients referred to the Sleep Disorders and Acupuncture Unit for polysomnography as part of the screening process for a sleep disorder. Only controls presenting an apnea-hypopnea index < 15/h, a periodic leg movements index during sleep < 15/h and a total sleep time ≥ 6 hours on the video-polysomnography will be analyzed.

Inclusion Criteria:

• The patient must have given their free and informed consent and signed the consent form

• The patient must be a member or beneficiary of a health insurance plan

• Ability to understand, write and read French Inclusion criteria for patients with major depression

• Diagnosis of depression according to DSM-5 criteria

• Suspicion of a sleep disorder requiring polysomnographic screening

• Score for IHSS items 3 and 4

  • Score ≥ 1 for group with sleep inertia
  • Score = 0 for the group without sleep inertia Inclusion criteria for controls

• No complaints of sleep inertia (score = 0 on IHSS items 3 and 4)

• No excessive daytime sleepiness (Epworth Sleepiness Scale score ≤10),

• No depressive symptoms (Hospital Anxiety Depression Scale score < 8 on items 2, 4, 6, 8, 10, 12, 14).

Exclusion Criteria:

• The patient is participating in an interventional study
• The patient is under safeguard of justice or state guardianship
• Unweaned from the following medications for at least 5 half-lives prior to inclusion: wake-promoting or psychostimulant drugs (modafinil, methylphenidate, mazindol, amphetamine, pitolisant, solriamfetol, sodium oxybate), neuroleptics, hypnotics, antidepressants, anxiolytics, antiepileptics, budipine, dopamine agonist and antagonist antiemetics (except domperidone), opiates, gabapentin, pregabalin, benzodiazepines, Z-hypnotics (zolpidem and zopiclone), monoamine oxidase inhibitors, catechol-O-methyltransferase or sedative antihistamines.
• Patients with central nervous system diseases: Parkinson's disease, mild cognitive impairment and dementia, progressive supranuclear palsy, multisystem atrophy, Huntington's chorea, amyotrophic lateral sclerosis, epilepsy, history of head trauma with loss of consciousness.
• Patients with a malignant neoplastic disease requiring therapeutic treatment in the 12months prior to the screening visit
• Other medical or psychiatric illnesses (with the exception of depression in he depression group) which, in the investigator's opinion, could interfere with the study.
• History of suicide attempt (including failed attempt), or suicidal ideation in the past month
• Chronic alcohol consumption or drug abuse in the previous 6 months
• Sleep-wake circadian rhythm disorders and presence of sleep insufficiency according to ICSD-3 criteria
• Pregnant, parturient or breast-feeding women.

The study population comprises three groups of 30 analyzable participants: patients with Major Depressive Disorder and sleep inertia, patients with Major Depressive Disorder and without sleep inertia, and controls without mood disorders or sleep inertia. Controls will be patients referred to the Sleep Disorders and Acupuncture Unit for polysomnography as part of the screening process for a sleep disorder. Only controls presenting an apnea-hypopnea index < 15/h, a periodic leg movements index during sleep < 15/h and a total sleep time ≥ 6 hours on the video-polysomnography will be analyzed.