The first week of summer. What the circadian reset actually feels like.

The first week of summer holiday produces a predictable pattern in my clinic. Parents brin...

The first week of summer holiday produces a predictable pattern in my clinic. Parents bring children who are sleeping late, reluctant to be active in the mornings, and irritable in ways that seem inconsistent with the freedom the holiday should be producing. The question is: what's wrong?

Nothing is wrong. This is the circadian reset. The school year imposes an external social clock on the child's biological clock — a fixed wake time, a fixed departure time, a fixed structure of alertness and activity. When that external clock disappears, the biological clock begins to drift toward its natural position. For most children, the natural position is about ninety minutes later than the school-year position. For adolescents, it can be three to four hours later. The first week of summer is the week the biological clock is finding its way home.

The drift produces the irritability. The child whose biological clock says 'seven in the morning' but whose social clock says 'you should be cheerful because it's the holidays' is experiencing a genuine mismatch. The irritability is the mismatch. It is not the holiday failing. It is the biology arriving.

The drift produces the irritability. The child whose biological clock says 'seven in the morning' but whose social clock says 'you should be cheerful because it's the holidays' is experiencing a genuine mismatch. The irritability is the mismatch.

What to do with the circadian reset is not to fight it, and not to let it run without bound. The reset has a useful middle period — approximately days four through ten — when the child's biological clock has settled into its natural position but hasn't drifted so far that September will be a crisis.

The advice I give families at this point: let the first three days run freely. Don't impose a wake time. Don't engineer morning activity. Allow the biology to find its position. By day four you will know what the child's natural sleep preference is. This is useful information. Most parents don't know it.

Days four through ten: maintain the natural wake time but introduce morning light. Fifteen minutes of outdoor time within the first hour of waking is the most effective circadian anchor available. It tells the biological clock what time of day it is without imposing a social time. The clock uses the light as information. The clock adjusts.

Day eleven onwards: the holiday has a rhythm. The child wakes within a predictable window, has energy at predictable times, and is sleeping at a time that, while later than school-year timing, is stable. This is the holiday homeostasis. Protect it. Don't over-schedule. The child's biology is resting. That rest is producing something — the creativity, the long games, the unexpected interests — that the school year was too busy to allow.

In late August, begin the gradual return: fifteen minutes earlier bedtime every two days. By September 1st the child should be within thirty minutes of school-year timing. The adjustment is much easier done gradually than in one overnight correction.

In late August, begin the gradual return: fifteen minutes earlier bedtime every two days. By September 1st the child should be within thirty minutes of school-year timing. The adjustment is much easier done gradually than in one overnight correction.

What is your child's natural sleep timing when there is no alarm and no school? Do you know this? And: does the first week of summer in your household tend to produce irritability that seems inconsistent with the freedom it brings? What is your interpretation of that irritability?

For the first three days of summer: no alarm, no engineered morning activities. Let the biology find its position. At day four: add fifteen minutes of outdoor morning time — not as exercise, as light. The light tells the clock what time it is.

Next week: Marian on what the long, unstructured July morning does to the developing brain — and why the boredom that arrives by day three is exactly what you were hoping for.

Names of people and brands in these editions are changed. Whoever was there and reads this knows what we are talking about.

Marian adds, from London: The biology Victor is describing has a specific mechanism worth naming: the school year produces what researchers call 'social jet lag' — a mismatch between the biological clock and the social clock. The first week of summer is the recovery from social jet lag. The irritability is the same irritability you'd feel after a transatlantic flight: the body is trying to find what time it actually is. Give it three days. It will find it. — Marian