The nap, the coffee and the sweet treat#

Commit first#

Rank these three by how well the evidence supports them.

1. a nap
2. a coffee
3. something sweet

Write your order down. One of them does the opposite of what almost everyone believes.

The nap, which works#

Rosekind and colleagues (1994) studied pilots on real long-haul transpacific flights, given a 40-minute rest opportunity in the cockpit.

They slept about 26 minutes on average, and showed clearly better vigilance and physiological alertness than the no-nap group. Still there through descent and landing.

A pedantic note, in keeping with this course#

The famous “34% better performance, 54% better alertness” numbers come from the team’s 1995 write-up in the Journal of Sleep Research.

Not the original NASA memorandum everybody links to.

Small thing. We care about it here.

The part that changes your behaviour#

Brooks and Lack (2006, Sleep) tested naps of 5, 10, 20 and 30 minutes in sleep-restricted people.

Two literatures, and one gap#

Mednick, Nakayama and Stickgold (2003, Nature Neuroscience) showed a nap can consolidate learning about as well as a night’s sleep. But that needs roughly 60 to 90 minutes, and it is a memory effect, not an alertness one.

Nobody has studied naps and rumination. Sleep on the loop and it might close is this course’s guess, not a finding.

The coffee, which is oversold#

Peter Rogers and colleagues (2010, Neuropsychopharmacology) tested 379 people after 16 hours without caffeine.

• habitual consumers given caffeine came back to baseline, with no net gain
• non-consumers did rise, and that was offset by increased anxiety and jitteriness

Rogers defended the position again in 2014. Contested rather than settled, but it reframes your morning coffee as maintenance rather than enhancement.

The anxiety risk, both sides#

In studies giving 400–750 mg to people with panic disorder, around half had a panic attack, against none on placebo. That is a large dose and a clinical population.

The honest counterweight. Hoppe and colleagues (2025, Journal of Psychopharmacology) gave a realistic 150 mg to panic-disorder patients and controls in a double-blind crossover, and found no increase in subjective anxiety. Contrary to their own hypothesis.

The sweet treat#

Mantantzis, Schlaghecken, Sünram-Lea and Maylor (2019, Neuroscience & Biobehavioral Reviews) meta-analysed 176 effect sizes from 31 studies and 1,259 participants.

• no positive effect on any aspect of mood, at any time point
• alertness lower within 60 minutes
• fatigue higher within 30 minutes

Before anyone gets smug#

This is a claim about sugar, not about treats.

If a biscuit and ten minutes away from your desk helps you, the plausible mechanism is the ten minutes, the ritual and the deliberate stop.

That route is unstudied, which is not the same as disproven. You had a break and credited the sugar.

What to reach for instead#

Move. Ensari and colleagues (2015, Depression and Anxiety) found single bouts of exercise reduce state anxiety by around a quarter of a standard deviation. Modest, not miraculous, and more than sugar manages.

Take a break that is actually a break. Week 5 found only undemanding activity produces incubation. Week 6 found a phone break measuring like no break at all.

Check your ranking#

• which of the three do you actually reach for, and what were you crediting it with?
• the treat finding is the clearest case in the course of a felt improvement that measures as the opposite. Where else have you got that wrong?
• what has genuinely helped this week, and can you tell it apart from what merely felt like it did?