Sleep restriction therapy — how it works

The protocol, step by step

Step 1 — measure baseline

Keep a simple sleep diary for one to two weeks. Record:

• What time you got into bed.
• What time you fell asleep (estimate).
• Any times you woke during the night and roughly how long.
• Final wake time and time out of bed.

Calculate average total sleep time (TST) and time in bed (TIB). Your sleep efficiency is TST / TIB.

Step 2 — set your sleep window

Pick a fixed wake time you can keep seven days a week. Your bedtime is whatever puts you in bed for the duration of your baseline total sleep time. Minimum 5 hours — go below this only with clinical supervision.

Example: if you slept an average of 6.2 hours over two weeks, and your fixed wake time is 7am, your initial sleep window is 00:45 to 07:00. You do not get into bed before 00:45, full stop.

Step 3 — stick to it for 7 days

This is the hard part. The first week is genuinely difficult — you'll be sleep-deprived during the day. That's the feature, not the bug: sleep pressure builds up rapidly, and within a few nights you'll be falling asleep within minutes and sleeping nearly the whole window.

• No daytime napping.
• If you can't sleep within ~20 minutes of getting in bed, get up (stimulus control). Return only when sleepy.
• Avoid alcohol entirely during the restriction phase.
• Get morning bright light to anchor wake time.

Step 4 — adjust weekly

At the end of each week, calculate your sleep efficiency:

• ≥ 90%: extend time in bed by 15 minutes (move bedtime earlier).
• 85–89%: hold the current window for another week.
• < 85%: reduce by 15 minutes (move bedtime later).

Repeat until you reach a window that matches your actual sleep need with efficiency consistently above 85%.

Why this works

Insomnia is, mechanistically, a problem of sleep consolidation — fragmented, inefficient sleep with excessive time in bed. Two forces consolidate sleep:

• Sleep pressure (adenosine accumulation) — higher pressure produces more consolidated sleep.
• The bed becoming a strong cue for sleep— which only happens if you consistently sleep there and don't spend long awake periods in bed.

Sleep restriction increases sleep pressure and re-conditions the bed at the same time. The trade-off — daytime sleepiness for 1–2 weeks — is real, but the resolution is fast and durable.

Common mistakes

• Cheating with naps. Even a 20-minute nap dramatically reduces sleep pressure and slows the protocol.
• Sleeping in on weekends. Defeats the entire protocol. Wake time must be fixed.
• Extending the window too early. Hold at high efficiency for at least a week before extending.
• Going below 5 hours unsupervised. Severe restriction can be unsafe and isn't necessary for most cases.

When to seek supervision

Strongly consider doing sleep restriction with a CBT-I therapist, app (Sleepio, Somryst), or clinician if:

• Your baseline sleep is under 5 hours.
• You have bipolar disorder or a history of mania.
• You have untreated sleep apnoea (treat that first).
• You drive professionally or operate machinery.
• You have severe depression with suicidal thoughts.