Psychological sleep disorders: Pathology review

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Psychological sleep disorders: Pathology review

Psychological disorders

Bipolar and related disorders

Bipolar disorder

Feeding and eating disorders

Anorexia nervosa

Bulimia nervosa

Medication-induced movement disorders and other adverse effects of medication

Neuroleptic malignant syndrome

Serotonin syndrome

Somatic symptom and related disorders

Factitious disorder

Somatic symptom disorder

Trauma and stressor-related disorders; Abuse

Physical and sexual abuse

Post-traumatic stress disorder


Psychological sleep disorders: Pathology review

USMLE® Step 1 questions

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USMLE® Step 1 style questions USMLE

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A 25-year-old graduate student comes to the physician for evaluation of excessive sleepiness over the past year. He is often sleepy during the day and frequently falls asleep during class. These episodes occur nearly daily and have been negatively affecting his grades. The patient goes to bed at 10 PM and wakes up at 7 AM. Last week, during an argument with his partner, the patient suddenly felt weak in the legs and collapsed onto the floor. The patient does not consume alcohol or recreational drugs. He has not experienced a loss of interest in his normal activities and does not have suicidal ideations. Vitals are within normal limits. Physical examination is unremarkable. Which of the following additional features is likely to be present in this patient?  


A 31 year old male named Hercules comes to the clinic complaining of excessive daytime sleepiness over the past year, despite getting a regular 7 to 9 hour sleep every night. This has recently started to interfere with his job, since he keeps dozing off at his desk, during meetings, or even while talking on the phone. Hercules is also concerned because he sometimes has very vivid dream-like sensations right before falling asleep, like seeing other people in the room. On further questioning, Hercules also mentions that when he gets really nervous or excited about something, he feels as if he cannot move his legs and might even fall down. Past medical history and physical examination are both unremarkable.

Based on the initial presentation, Hercules seems to have some form of sleep disorder. Many of us can have trouble falling asleep or may sleep too much from time to time, usually because of stress or a temporary illness. But when sleep problems become a regular occurrence and interfere with daily life, that’s a sign of a sleep disorder. For your exams, remember that sleep disorders are usually caused by factors that interrupt the sleep cycle, which is a period of sleep that lasts about 90 minutes and is divided into four stages. The first three stages make up non-REM or NREM sleep, which stands for non-rapid eye movement. So usually during non-REM sleep, our eyes don’t move much or at all. However, keep in mind that the voluntary muscles of the body may still be active. NREM sleep accounts for roughly 80% of the sleep cycle, and across the three stages of NREM, we move from very light sleep during Stage 1, to very deep sleep in Stage 3. This is followed by Stage 4, which is known as rapid eye movement or REM sleep, and accounts for the last 20% of the sleep cycle. During REM sleep, the eyes dart around really fast, and this is where dreaming occurs and memories are consolidated. During REM sleep, the voluntary muscles of the body are paralyzed, probably to prevent people from acting out their dreams. Now, REM sleep is then followed again by non-REM sleep, and over the course of the night, there are four or five of these sleep cycles.

Okay, now for your test, the most high yield sleep disorders include sleep terror disorder, enuresis, and narcolepsy.

Let’s start with sleep terror disorder.

For your exams, remember that this is typically triggered by stress or fatigue, fever, or sleep deprivation, and is most common in children. So, in sleep terror disorder, individuals partially wake up during deep sleep or stage 3 of NREM sleep, and suddenly start screaming or crying. And this turns on the sympathetic nervous system, which can lead to mydriasis or dilated pupils, tachycardia or rapid heart rate, tachypnea or rapid breathing, and sweating. What’s extremely high yield is that individuals usually return to sleep right afterwards, and the next day they have no recollection of the episode. For your exams, make sure you're able to set sleep terrors apart from nightmares, which typically occur during REM sleep, and individuals wake up right away and the next day, they are able to recall the episode! Okay, now, because sleep is disrupted, people with sleep terror disorder often feel chronically fatigued, which can lead to distress and impairment in a person’s life. Good news is that sleep terror disorder is typically self limited and tends to resolve spontaneously by puberty, so no treatment is needed.


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  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "Diagnostic and Statistical Manual of Mental Disorders" NA (1980)
  5. "Sleep disorders" Neurobiology of Psychiatric Disorders (2012)
  6. "Family history of REM sleep behaviour disorder more common in individuals affected by the disorder than among unaffected individuals" Evidence Based Mental Health (2013)
  7. "Sleep: A Novel Mechanistic Pathway, Biomarker, and Treatment Target in the Pathology of Alzheimer's Disease?" Trends in Neurosciences (2016)

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