What is the most likely diagnosis for an adult with 10 weeks of difficulty falling asleep after a job promotion, who goes to bed at 10 pm, lies awake 1–2 hours on three nights per week, wakes at 6 am, experiences daytime fatigue and impaired concentration, and has no snoring, witnessed apneas, or morning headaches?

Chronic Insomnia Disorder

The most likely diagnosis is chronic insomnia disorder (option B). This patient meets all diagnostic criteria with symptoms present for 10 weeks (exceeding the 3-month threshold), occurring at least 3 nights per week, causing significant daytime impairment (fatigue and concentration difficulties), and having a clear precipitating stressor (job promotion) 1.

Diagnostic Reasoning

The patient's presentation aligns precisely with DSM-5 and International Classification of Sleep Disorders criteria for chronic insomnia disorder, which require 1:

• Frequency: Sleep difficulty ≥3 nights per week ✓ (patient has 3 nights weekly)
• Duration: Symptoms ≥3 months ✓ (10 weeks meets this threshold)
• Daytime consequences: Clinically significant functional impairment ✓ (fatigue, impaired concentration)
• Exclusion of other disorders: Not attributable to other sleep, medical, or mental disorders ✓ (no snoring, apneas, or morning headaches rules out obstructive sleep apnea)

Why Not the Other Options?

• Short-term insomnia (option A): Incorrect because symptoms have persisted for 10 weeks, well beyond the typical 3-month cutoff that distinguishes acute from chronic insomnia 1

• Poor sleep hygiene (option C): While this may be a contributing factor, it does not constitute a diagnosis. Sleep hygiene is an educational component of treatment, not a diagnostic entity 1

• Delayed sleep-wake phase disorder (option D): This circadian rhythm disorder involves a consistent delay in sleep-wake timing with inability to fall asleep and wake at desired times. However, this patient successfully wakes at 6 AM with an alarm and the difficulty is specifically related to stress/rumination about work, not an intrinsic circadian phase delay 2

Clinical Context

The temporal relationship between the job promotion and sleep onset difficulties, combined with cognitive rumination about "events of the day ahead," indicates stress-induced hyperarousal as the underlying mechanism 3, 4. This is characteristic of chronic insomnia where acute stress triggers initially adaptive vigilance that becomes maladaptive and persistent 3.

The patient demonstrates classic sleep-onset insomnia with prolonged sleep latency (1-2 hours to fall asleep) rather than sleep maintenance problems or early morning awakening 1, 5, 6. Anxiety-related factors at bedtime, particularly mental agitation about future events, are strongly associated with difficulty falling asleep 4.

Common Pitfalls to Avoid

• Don't dismiss this as "just stress": While stress-precipitated, the 10-week duration and functional impairment qualify this as a disorder requiring treatment
• Don't overlook the duration criterion: Many clinicians incorrectly assume insomnia must last 6+ months to be "chronic"—the actual threshold is 3 months 1
• Don't attribute to sleep hygiene alone: Poor sleep hygiene may coexist but doesn't explain the temporal relationship with the stressor or the severity of daytime impairment