Sleep hygiene

What the research says

Sleep deprivation is used as a form of torture. That alone tells you something about how essential it is. During sleep, your brain runs a series of critical processes it simply cannot do while you're awake:

• Glymphatic clearance: your brain's waste-removal system is almost exclusively active during sleep, clearing metabolic byproducts including those associated with brain injury
• Memory consolidation: converting experiences from short-term to long-term storage
• Hormonal regulation: growth hormone, cortisol, and reproductive hormones are all managed during sleep cycles
• Muscle and tissue repair: the body's physical recovery happens predominantly at night
• Nervous system reset: sleep is the primary mechanism for restoring balance between sympathetic and parasympathetic function

Your sleep cycle starts when you wake up

One of the most useful things I've come across in neuroscientist Andrew Huberman's work on sleep is this: your sleep that night is largely determined by what you do in the first hour of the morning. The two key mechanisms are adenosine and cortisol.

Adenosine is a chemical that builds in your brain from the moment you wake. The longer you're awake, the more adenosine accumulates, and the more sleep pressure you feel. Caffeine works by temporarily blocking adenosine receptors, not by adding energy. This is why the crash hits when caffeine wears off: all that built-up adenosine floods in at once.

Cortisol gets a bad reputation as the stress hormone, but a healthy cortisol spike in the morning is essential. It's what actually wakes you up properly, sharpens focus, and sets your internal clock for the day. The problem only arises when cortisol spikes at the wrong times, like late at night.

Huberman also recommends delaying your first caffeine by 90 to 120 minutes after waking, letting your natural cortisol do its job first before using caffeine to extend alertness later in the morning.

A note on caffeine and neurodivergence

The standard advice around caffeine and sleep assumes a neurotypical nervous system. For people with ADHD, the picture is often quite different. Stimulants, including caffeine, can have a paradoxical calming effect because they boost dopamine in a way that helps regulate what is essentially an underactivated system. Some people with ADHD genuinely sleep better after an evening coffee. This isn't a myth or a quirk. It's a different neurological response to the same substance.

If you're neurodivergent and the caffeine rules don't match your experience, trust your experience. The goal is understanding your own patterns, not fitting someone else's template.

What actually helps

In the evening

• Avoid screens for at least an hour before bed. Blue light suppresses melatonin, the hormone your body needs to initiate sleep. Blue light glasses or night mode settings help if screens are unavoidable.
• Wind down with something low-stimulation: music, drawing, puzzles, gentle conversation, reading a physical book.
• Dim your lights. Bright overhead lighting signals daytime to your nervous system. Candles or low lamps start the transition.
• Avoid caffeine and sugar in the afternoon. Caffeine has a half-life of around 5 to 6 hours. A 3pm coffee is still partly active at 9pm. For most people. See above for ADHD.
• Herbal tea or warm milk. Milk contains tryptophan, a precursor to melatonin. Tart cherry juice is naturally high in melatonin.
• Melatonin supplements. Available on prescription in New Zealand, not currently subsidised. Worth discussing with your GP if sleep disruption is significant.
• Do a sleep meditation. Calm, Headspace, Balance, or YouTube all have good options.
• Write down tomorrow's tasks. Getting them out of your head and onto paper frees your brain from keeping the list active overnight.

Across the day

• Get outside in the morning light within 30 to 60 minutes of waking. Even on cloudy days. This is the single highest-leverage habit.
• Get up at the same time every day, even on weekends. Consistent wake time anchors your sleep-wake cycle.
• Limit naps to 20 minutes and avoid them after 3pm. Longer naps reduce sleep pressure overnight.
• Gentle exercise in the morning or early afternoon. Vigorous evening exercise raises adrenaline and body temperature, both of which interfere with sleep onset.
• Room temperature around 18 degrees. A cooler environment supports the body's natural temperature drop that accompanies sleep onset.

Sleep affirmations

If your mind races when you lie down, affirmations can help redirect it:

• I know I did my very best today.
• I can feel myself relaxing.
• I am worthy of rest.
• I deserve a good night's sleep.
• I will sleep restfully and wake restored.

Further reading

Andrew Huberman's podcast episodes on sleep are some of the most practical and research-grounded resources available. His episode Master Your Sleep and Be More Alert When Awake is a good starting point. Available free on all podcast platforms and YouTube.