Insomnia vs. a “Late Body Clock”: A Quick Sorting Guide

Insomnia vs. a “Late Body Clock”: A Quick Sorting Guide

When you’re exhausted and wide awake at 2 a.m., insomnia vs delayed sleep phase can feel identical. Clinically, though, they’re different problems that respond to different tools: CBT‑I for true insomnia, and a circadian timing plan (morning light + fixed wake time ± precisely timed low‑dose melatonin) for a late body clock (also called delayed sleep‑wake phase disorder/DSWPD). Matching the pattern to the plan is how you get traction fast (1)(2)(3).

🧭 Key takeaway: Getting the right match—CBT‑I for insomnia; light‑and‑timing for a late clock—saves time, effort, and frustration.

Along the way, if anxiety, trauma, OCD, ADHD, or neurodivergence are in the mix, a blended plan often works best. Our team can help you sort this and build a plan. You can schedule a free consultation with Ryan Robertson to get started.

Why this matters

Many “insomnia” cases are really a late body clock. When you apply sleep compression and “go to bed on time” to a circadian problem, you can make nights worse. When you apply light‑and‑timing to hyperarousal‑driven insomnia, you can miss the mark.

Right match = faster results:

• CBT‑I for insomnia patterns (1)(2)

• Morning light, fixed wake‑time, and evening dimming for late‑clock patterns (3)(4)

🎯 Key takeaway: If sleep is solid on your preferred (later) schedule but falls apart when you try to sleep early, think circadian, not behavioral insomnia.

The 3‑question quick sort

1. If you could set your own schedule, would you sleep well?

   “Yes” → likely late body clock.

   “No” → likely insomnia.

   
   

2. How different are weekdays vs. weekends?

   Look at sleep midpoint or wake‑time shift. A ≥2‑hour later weekend midpoint or wake‑time leans late body clock.

   
   

3. What happens on vacation?

   Sleep drifts later but feels solid → late clock.

   Still fragmented → insomnia.

🕰️ Key takeaway: A big weekday‑weekend gap (social jet lag) and better sleep on late schedules both point to a circadian delay (3).

How to evaluate a 7‑day sleep log

Use the Consensus Sleep Diary format if possible (5). When reading logs, these clues help:

Insomnia clues

• Sleep onset latency (SOL) > 30 minutes repeatedly (6)(7)

• Wake after sleep onset (WASO) > 30–45 minutes (6)(7)

• Variable nights, “trying hard” to sleep, early or middle awakenings even when the schedule is free

• Sleep feels light/fragmented and often stays fragmented even when you try a later bedtime

  
  

Late‑clock clues

• Falls asleep easily when late; struggles only when trying to go to bed earlier

• Long, solid sleep (often 8–10+ hours) if allowed to wake late

• Very hard morning wake‑ups; large weekend drift

• Sleep consolidates quickly when you set a fixed wake time and get morning outdoor light (3)(4)

📊 Key takeaway: SOL/WASO thresholds help flag insomnia; timing‑dependent ease of sleep points to a circadian delay (5)(6).

If you’re unsure, consider a brief psychological assessment to clarify overlapping issues (e.g., anxiety, ADHD) that can complicate sleep.

FAQ

Is melatonin always necessary for a late clock?

No. Many people advance well with morning light + fixed wake. If used, low‑dose melatonin (≈0.5 mg) is typically early evening, not at bedtime, and should be clinician‑guided (8).

Can I mix CBT‑I and circadian steps?

Absolutely. Many clients do best with a circadian anchor first, then layer CBT‑I elements to reduce worry and build confidence (1)(3).

What if I “sleep fine on weekends but not weekdays”?

That’s a classic delayed schedule clue; start the circadian timing track (3)(9).

Disclaimer

This article is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or qualified health provider with questions about a medical condition. Individual results may vary.

References and Citations

(1) Edinger, J. D., Arnedt, J. T., et al. (2021). Behavioral and psychological treatments for chronic insomnia disorder in adults: An American Academy of Sleep Medicine clinical practice guideline. Journal of Clinical Sleep Medicine, 17(2), 255–262. https://doi.org/10.5664/jcsm.8986

(2) Qaseem, A., Kansagara, D., Forciea, M. A., Cooke, M., & Denberg, T. D. (2016). Management of chronic insomnia disorder in adults: A clinical practice guideline from the American College of Physicians. Annals of Internal Medicine, 165(2), 125–133. https://doi.org/10.7326/M15-2175

(3) Auger, R. R., Burgess, H. J., Emens, J. S., et al. (2015). Clinical practice guideline for the treatment of intrinsic circadian rhythm sleep‑wake disorders: Advanced sleep‑wake phase disorder (ASWPD), delayed sleep‑wake phase disorder (DSWPD), non‑24‑hour sleep‑wake rhythm disorder (N24SWD), and irregular sleep‑wake rhythm disorder (ISWRD). Journal of Clinical Sleep Medicine, 11(10), 1199–1236. https://doi.org/10.5664/jcsm.5100

(4) Crowley, S. J., & Eastman, C. I. (2014). Phase advancing human circadian rhythms with morning bright light, afternoon melatonin, and gradually shifted sleep. Journal of Clinical Sleep Medicine, 10(1), 49–62. https://doi.org/10.5664/jcsm.3328

(5) Carney, C. E., Buysse, D. J., Ancoli‑Israel, S., Edinger, J. D., Krystal, A. D., Lichstein, K. L., & Morin, C. M. (2012). The Consensus Sleep Diary: Standardizing prospective sleep self‑monitoring. Sleep, 35(2), 287–302. https://doi.org/10.5665/sleep.1642

(6) Schutte‑Rodin, S., Broch, L., Buysse, D., Dorsey, C., & Sateia, M. (2008). Clinical guideline for the evaluation and management of chronic insomnia in adults. Journal of Clinical Sleep Medicine, 4(5), 487–504. https://doi.org/10.5664/jcsm.27286

(7) Edinger, J. D., et al. (2013). Sensitivity and specificity of polysomnographic criteria for defining insomnia. Journal of Clinical Sleep Medicine, 9(5), 481–491. https://doi.org/10.5664/jcsm.2672

(8) Burgess, H. J., Revell, V. L., Molina, T. A., & Eastman, C. I. (2010). Human phase response curves to three days of daily melatonin: 0.5 mg versus 3.0 mg. Journal of Clinical Endocrinology & Metabolism, 95(7), 3325–3331. https://doi.org/10.1210/jc.2009-2590

(9) Crowley, S. J., Acebo, C., & Carskadon, M. A. (2007). Sleep, circadian rhythms, and delayed phase in adolescence. Sleep Medicine, 8(6), 602–612. https://doi.org/10.1016/S1389-9457(06)00707-6

(10) Gradisar, M., Dohnt, H., Gardner, G., et al. (2011). Randomized controlled trial of CBT plus bright light therapy for adolescent delayed sleep phase disorder. Sleep, 34(12), 1671–1680. https://doi.org/10.5665/sleep.1432

(11) Ong, J. C., Crawford, M. R., et al. (2020). Sleep apnea and insomnia: Emerging evidence for effective clinical management of comorbid insomnia and sleep apnea (COMISA). Nature and Science of Sleep, 12, 133–148. https://doi.org/10.2147/NSS.S238673