Behavioural insomnia and circadian rhythm disorders — structured clinical encounter

Station brief (candidate)

You are the paediatric registrar in a general clinic. A 15-year-old boy is referred with worsening school lateness and absence over six months. He describes lying awake until about 2am despite trying to sleep earlier, being impossible to rouse for school, and feeling sleepy and irritable through the morning that improves by the afternoon. At weekends and in holidays he sleeps from around 2am to 11am and wakes refreshed. His mother asks whether he is depressed or just lazy. The team asks you to establish the diagnosis, assess him, exclude organic and mood disorder, and plan treatment. You have 12 minutes with the family and 5 minutes for examiner discussion. [8] [9]

Information available on request

• Sleep diary over two weeks: consistent sleep onset around 2am and, on free days, wake around 11am with refreshing sleep; on school days he is woken at 7am after about five hours and is very sleepy. [8]
• No snoring, gasping or witnessed apnoeas; no restless legs or urge to move at rest; no cataplexy or sleep attacks. [8]
• Screen-based device use in bed until late; caffeine energy drinks in the evening. [9]
• Mood screen (on request): low mood and frustration attributed to missing school and conflict at home; no anhedonia, no hopelessness, and no suicidal ideation on direct questioning. [9]
• Examination: normal growth and general examination; no goitre or focal neurology. [8]
• Actigraphy (on request, if available): confirms a stably delayed sleep-wake pattern. [8]

Tasks

1. Give the diagnosis and the features that support it, and explain why it is not simply laziness. [8] [9]
2. Outline your assessment and the two things you must actively exclude or screen for. [8]
3. State your management plan, including how melatonin and light should be timed and why. [8] [6]
4. Explain the role of the school and the risk of relapse. [9]

Marking anchors

Must-hit

• Diagnoses delayed sleep-wake phase disorder from the stable late sleep onset, the great difficulty waking for school, and the normal refreshing sleep of normal length on the delayed weekend schedule; explains that this is a biologically driven late clock (the adolescent perfect storm) worsened by evening light, screens and caffeine, not laziness. [8] [9]
• Assesses with a sleep history and a one to two week sleep diary (actigraphy if available), confirms adequate sleep opportunity, actively excludes an organic sleep disorder (no snoring or restless legs) and actively screens for depression, anxiety and suicidal ideation. [8]
• Plans a fixed daily wake time, sleep hygiene with reduced evening light and screens, timed morning bright light, and low-dose evening melatonin given several hours before habitual sleep onset to act as a chronobiotic (not a large bedtime hypnotic), citing the AASM circadian guideline and the light-plus-melatonin evidence. [8] [11]

Merit

• Explains that melatonin timing matters more than dose in delayed phase, engages the school to support a graded return and adjusted timing, warns that the phase relapses if the routine lapses (weekend sleep-ins), and reserves chronotherapy and specialist referral for refractory cases. [6] [8]

Fail

• Labels the adolescent lazy or depressed without a sleep assessment, or simply advises an earlier bedtime without morning light and correctly timed melatonin, so the intervention fails. [9]
• Prescribes a sedative or a large bedtime dose of melatonin as a hypnotic, losing the clock-shifting effect and missing a possible mood disorder. [8]