Phone-Free Bedroom — Body Handbook

Sleep · §185

Phone-Free Bedroom

The phone on the nightstand is the single sleep-hygiene mistake most people fix last and should fix first. Even silent and face-down it pulls attention; its light delays the body clock; the first thing your hand touches in the morning sets the day's stress floor. The fix is structural — phone out of the bedroom, a cheap alarm clock or dawn lamp in its place, no phone in the first hour after waking.

Do · Daily Evidence Emerging Chapter Sleep

You fall asleep faster, stay asleep longer, and wake up to your own morning instead of someone else's notifications. The hardest part is the first two weeks — your hand will reach for a phone that isn't there. After that the rule runs itself, and the first hour of the day is yours again. It costs the price of an alarm clock and no willpower past the setup, because the phone is somewhere you can't reach it. That's the whole trick.

Why a phone in the bedroom does the damage it does

Four pathways, all real, all triggered the moment the phone is within reach.

Light. A phone screen pushes blue-enriched light at about 30 to 50 lux from the angle you hold it. Cells in the eye that don't see images but do track brightness send that signal straight to the body clock. In the evening, the body reads "still daytime" and pushes melatonin onset later — exposure to ordinary indoor light alone has been shown to shorten the body's melatonin window by roughly 90 minutes Gooley 2011, and a tablet-style screen read for a few hours before bed does the same Chang 2015.

The phone is loud even when it's silent. A study at the University of Texas put participants' own phones face-down on the desk and measured working memory; performance was worse than when the phone was in the next room, even though nobody touched it Ward 2017. The brain spends background bandwidth tracking it. At sleep onset you need the opposite of background bandwidth.

Overnight micro-arousals. Vibration, a glow on the wall, an anticipated message — these fragment sleep in ways you don't remember in the morning but a sleep lab can measure. Even on do-not-disturb, the device's mere proximity preserves a thread of vigilance.

The first hour. The 30 to 45 minutes after waking are when the body stages the day's cortisol response Clow 2010 Fries 2009. Opening email, social feeds, or news inside that window front-loads the day's stress into the moment your nervous system is most receptive to it. Whether the result is an acute spike or, over time, a flattened response, the felt experience is the same: you walked into a meeting before you woke up.

What the data shows

The mechanism evidence is strong; the trial evidence in adults is thinner but consistent. In a four-week trial, young adults who took their phones out of the bedroom slept longer, slept better, scored higher on working memory, and reported steadier mood than the control group He 2020. A representative survey of 844 adults found a dose-response gradient: more bedtime phone time meant later bedtimes, longer time to fall asleep, and shorter total sleep Exelmans 2016. A replication in university students showed the same pattern Pham 2021.

The denser dataset is in adolescents — younger users with higher phone-use intensity. A review covering more than 125,000 young people found that having a phone within reach at bedtime roughly doubled the odds of inadequate sleep, whether or not it was actively used Carter 2016 Hale 2015. Adults aren't adolescents, but the body clock and the working-memory pathway don't change with age — and the strongest predictor was bedside access, not use, which lines up with the silent-phone-on-the-desk result above.

The American Academy of Sleep Medicine recommends removing electronic devices from the bedroom as a standard sleep habit AASM 2017. That's consensus, not a verdict from a large adult trial — the large adult trial hasn't been run. The case rests on converging mechanisms, a clean small trial, and a body of observational data all pointing in the same direction.

What keeps happening if it stays on the nightstand

The version of you that goes to bed scrolling and wakes up to email is the version your partner stops asking whether you slept badly because the answer is always the same. You lose twenty to forty minutes of sleep most nights — not enough to notice on any single one, enough to compound across a year Exelmans 2016 Chang 2015. The afternoon you've been calling the slump stays the slump. The first hour of work that used to be your best hour gets done in the third hour at half the quality, because the first hour was spent reacting to an inbox Lanaj 2014. The meetings you used to walk into loose, you walk into braced.

None of it is dramatic. It's a slow widening of the gap between the day you wanted and the day you got. Over years, the well-documented consequences of chronic short sleep — mood instability, metabolic drift, immune fragility — find the same people Walker 2017.

How to do it

The mechanism is structural, so the protocol is too: make checking impossible, not optional.

Phone out of the bedroom an hour before bed, retrieved an hour after waking. Charger in the kitchen, the hallway, any room that isn't yours.
Standalone alarm clock or a dawn-simulation lamp. A cheap battery clock is fine; a dawn lamp (Lumie, Philips, Hatch — $60 to $200) replaces the alarm with a gradually brightening light, which independently improves morning alertness and lowers sleep inertia Gabel 2013 Thompson 2014.
Decide before you start what fills the first hour. Water, daylight, movement, breakfast, a written plan for the day — when the gap has shape, the reach for the phone has nothing to land on.
A book on the nightstand handles the "I need something to do" reflex the first few nights.
Emergency bypass if you need one. Most phones let starred contacts ring through do-not-disturb; a phone in the next room is still audible for a real emergency.

The first two weeks are the work. Your hand will reach for a phone that isn't there. Past two weeks the routine is mostly self-sustaining; past a month, most people don't want the phone back.

What doesn't actually work

Three fixes look like they should work and don't, because all three leave the phone in the room.

Night mode and blue-light filters. Software warm-shift modes reduce short-wavelength emission a little. They do nothing about content — the part of the phone that pulls you in — and they reduce the melatonin effect, not eliminate it.

Do-not-disturb mode. Silencing the night cuts notification-driven micro-arousals. It doesn't cut the silent cognitive pull of a phone within reach Ward 2017, and the phone is still the first thing you touch in the morning when you dismiss the alarm — at which point the rule has already broken.

"I just use it to read." The Brigham study controlled for exactly this — same readers, same room, same time, alternating between a light-emitting screen and a paper book. The screen pushed melatonin onset back about ninety minutes; the book didn't Chang 2015. The screen itself is the problem, not what's on it.

Where this goes wrong in practice

The dominant failure pattern is the half-measure: the phone stays in the room "for the alarm only." It rarely stays that way. Dismissing the alarm becomes a check; the check becomes a scroll; the scroll becomes a habit you stopped noticing. The structural fix is to take the alarm function off the phone — that's why a standalone clock matters more than it sounds.

The second pattern is substitution. Phone out, tablet in. iPad on the nightstand. Laptop for "one episode." The mechanism doesn't care which screen it is. Anything that emits light and accepts input belongs out of the bedroom.

Adjacent fixes — they stack, they don't substitute

Dim, warm light in the evening reduces melatonin suppression Gooley 2011 but doesn't touch the cognitive arousal arm. A consistent wind-down routine — any non-screen pre-sleep ritual — reduces pre-sleep arousal but doesn't fix the morning side. Morning sunlight inside the first hour does much of what a dawn lamp does and reinforces the next night's signal. None of these replaces phone-free bedroom; in practice they stack with it.

When you can't fully unplug

Some people are on call by job or by family. The intervention's structural goal — phone not the last touch of the night, not the first of the morning, not within hand-reach of the bed — can be preserved without going fully silent.

What the change buys you

Week one. You fall asleep faster on most nights. You wake up to whatever you set instead of an open phone an inch from your face. Mornings get back a slow, deliberate quality they don't have when the first thing you read is a Slack notification.

Weeks two to four. Sleep duration consolidates. The afternoon flat-line gets smaller. The four-week adult trial saw measurable improvements in sleep quality, mood, and working memory at this point He 2020. The people around you start asking what changed.

Month one onward. The first hour of the morning stops being a thing you have to defend — it's just the shape of the morning. The work you used to do worst because you started reactive, you start doing first. The version of you your partner sees in the evening is less braced, less skimming, more there.

Long-run cardiometabolic, mood, and skin effects are downstream of restored sleep itself Walker 2017 Adam 2017; the phone-free piece is a doorway into that, not a separate prize.

Related entries

Three pieces live next to this one and reinforce it: morning sunlight for the circadian entrainment a dawn lamp partly substitutes for; evening light reduction for the broader case the phone is one example of; and a consistent wind-down routine for the pre-sleep arousal piece. Sleep debt is where the cumulative cost of getting this wrong eventually shows up.

Related in the handbook

Helps

— The biggest reason a phone-free bedroom matters: it kills the late-night scroll that quietly eats into your sleep.
— A phone-free bedroom mostly works by removing the feed at the worst hour — it's news rationing applied to your sleep.

— The reason the phone is so hard to leave on the nightstand is that the apps are engineered to hold you.
— The real bedroom problem isn't radiation — it's the screen light and alerts, which leaving the phone out solves.
— The same trick that protects your sleep protects your focus: a phone in another room stops eating attention you don't notice losing.
— A phone in reach is the slot machine by your bed — distance is the structural fix, not willpower.
— A phone-free morning is what makes dream journaling possible; the notebook only works if the phone isn't there.
— Phone light at bedtime delays your clock — getting it out of reach is part of the same wind-down.
— A phone in reach also lights the room at night; pair charging it elsewhere with blackout curtains for a genuinely dark bedroom.
— If the phone isn't the first thing your hand finds, stepping into morning light becomes the natural way to start the day instead.

Substance and claimed effects

The intervention has three operationalised components: (1) the smartphone is physically removed from the bedroom from approximately one hour before sleep until at least one hour after waking; (2) a standalone alarm clock or dawn-simulation lamp replaces the phone's alarm function; (3) the first hour after waking is conducted without inbound digital input. The intervention is most often packaged as a sleep hygiene measure, but its plausible effects span evening light exposure, sleep-onset latency, total sleep time, fragmentation by overnight notifications, the cortisol awakening response (CAR), the first-hour stress and attention profile, and downstream effects on daytime affect, focus, and bedtime-routine consistency. The article projection from this dossier covers all of those consequences holistically.

Evidence by addressing question

mechanism

Evening light and melatonin. Smartphone screens emit short-wavelength (blue-enriched) light at illuminances of 30–50 lux at typical viewing distance. The melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs) project to the suprachiasmatic nucleus and suppress nocturnal melatonin secretion in a dose-dependent fashion. Gooley and colleagues demonstrated that exposure to <200 lux of indoor room light for eight hours before habitual bedtime shortens melatonin duration by approximately 90 minutes and suppresses peak melatonin by >50% in some subjects Gooley et al. 2011. Chang et al. showed in a within-subjects crossover that four hours of light-emitting eReader use before bed (compared with a print book) delayed dim-light melatonin onset by approximately 90 minutes, lengthened sleep-onset latency by ~10 minutes, suppressed evening sleepiness, and degraded next-morning alertness for several hours Chang et al. 2015.

Cognitive arousal from content. Independent of light, the content displayed on a smartphone — messages, social feeds, news, work email — is engineered for engagement and reliably elevates pre-sleep cognitive arousal. The mere presence of one's own smartphone within reach has been shown to reduce available cognitive capacity even when the device is silent and face-down Ward et al. 2017, suggesting an ongoing attentional pull that persists into the pre-sleep transition. Sleep-onset requires a deactivation of cortical arousal that is incompatible with task-positive engagement.

Sleep fragmentation. Overnight notifications, vibration, and ambient screen glow produce micro-arousals invisible to the user but detectable in polysomnography. Even when the phone is set to silent, the anticipation of an incoming message preserves vigilance.

Cortisol awakening response. The CAR is a 50–75% rise in salivary cortisol during the first 30–45 minutes after waking, distinct from the diurnal slope Clow et al. 2010 Fries et al. 2009. It is sensitive to anticipated demands of the upcoming day and is blunted in chronic stress and depression and exaggerated in acute stress. Checking a phone within seconds of waking front-loads an information cascade (work email, social comparison, news) into the window during which the HPA axis is staging the day; the mechanistic prediction is either potentiation (acute stress) or, with chronic exposure, dysregulation of the CAR's amplitude and slope. Direct human trials of phone-checking versus phone-deferral on CAR are sparse; the inference is mechanistic.

Dawn simulation. Replacing a phone alarm with a gradual-increase dawn-simulation light operates on the same ipRGC pathway as natural sunrise. Gabel and colleagues showed in a within-subjects crossover that artificial dawn (compared with dim light) improved well-being and cognitive performance during the first hour after waking and shifted cortisol secretion earlier Gabel et al. 2013. Thompson and colleagues showed reductions in sleep-inertia markers and improvements in post-waking performance with dawn simulation Thompson et al. 2014.

evidence

Bedtime mobile-phone use and sleep outcomes. In a representative survey of 844 Flemish adults, Exelmans and Van den Bulck found bedtime mobile-phone use after lights-off was prospectively associated with later bedtime, longer sleep-onset latency, shorter total sleep time, and worse self-rated sleep quality, with an exposure-response gradient Exelmans & Van den Bulck 2016. Pham and colleagues replicated the association in university students Pham et al. 2021. The adolescent literature is denser: Hale and Guan's systematic review of 67 studies in school-aged children and adolescents found a consistent association between screen use and shorter sleep duration, later bedtime, and worse sleep quality in roughly 90% of studies Hale & Guan 2015. Cain and Gradisar reached the same conclusion in their earlier review Cain & Gradisar 2010. Carter and colleagues' meta-analysis of portable-screen access and use in children and adolescents reported an approximate doubling of odds of inadequate sleep among bedtime device users (OR ~2.2 for use; OR ~1.8 for access without use) Carter et al. 2016. The bedside-presence-without-use effect is notable: simply having the phone within reach predicts worse sleep, consistent with the mere-presence mechanism.

Randomised restriction. He and colleagues ran a parallel-group RCT in which 38 young adults restricted bedtime mobile-phone use for four weeks. Restriction improved sleep quality (Pittsburgh Sleep Quality Index), sleep duration, positive affect, and working-memory performance compared with control He et al. 2020. The sample is small and short, but it is the cleanest causal evidence pointing in the predicted direction.

Late-night use and next-morning depletion. Lanaj and colleagues found that smartphone use after 9pm for work purposes predicted poorer next-morning self-control and engagement at work, with sleep partially mediating the effect Lanaj et al. 2014. The chain (evening phone → sleep degradation → next-day function) is empirically supported, not merely inferred.

Practice and guidance. The American Academy of Sleep Medicine's healthy-sleep-habits guidance recommends removing electronic devices from the bedroom AASM 2017. The recommendation is consensus-based, not RCT-backed, and rests on the body of mechanistic and observational evidence above.

Limit of the evidence. No large, long-duration RCT has tested the full intervention (bedroom removal plus standalone alarm plus first-hour deferral) against a credible active control on hard sleep endpoints in a representative adult population. The case rests on (a) the converging mechanism evidence (melatonin, mere presence, dawn-simulation), (b) consistent observational signal in adults, (c) a denser adolescent literature supporting the same effect, (d) one small adult RCT, and (e) clinical-guideline endorsement.

protocol

The minimal effective protocol comprises three components. The phone is placed outside the bedroom approximately 60 minutes before intended sleep onset and retrieved no earlier than 60 minutes after waking. A standalone alarm clock (or a dawn-simulation lamp with an alarm function, e.g. Lumie, Philips Wake-Up Light) replaces the phone alarm. The first waking hour is dedicated to non-digital morning activities (water, light exposure, movement, breakfast, planning) before the phone is opened. Dose-response evidence in this domain is coarse, but in the observational literature the gradient runs continuously: any reduction in bedtime phone exposure tends to improve sleep, and full removal outperforms partial measures (do-not-disturb mode, screen filters) that leave the device within reach.

Lower-friction variants exist: locking the phone in a drawer in another room, using a hardware lockbox with a timer, or having a partner hold it. Software-only mitigations (greyscale, app limits) ignore the mere-presence mechanism and are likely to under-deliver on the cognitive component Ward et al. 2017.

contraindications

None pharmacological. The single practical contraindication is on-call responsibility: physicians, parents of young or medically fragile children, primary caregivers of an unwell elderly relative, and shift-workers expecting urgent contact need an audible bypass for emergency calls (most phones permit a starred-contact bypass of do-not-disturb mode while the device is in another room). For most adults, a one-room separation is sufficient; the phone remains audible for true emergencies. No evidence of harm from the intervention itself.

misconceptions

Three widely repeated mitigations under-perform their reputation. (1) Night-mode / blue-light filters: software warm-shift modes reduce short-wavelength emission modestly but do not eliminate the melatonin-suppressive effect at typical illuminances, and they do nothing about cognitive arousal from content. The evidence base on f.lux-style filters for sleep outcomes is thin and not strongly positive. (2) Do-not-disturb mode: silencing notifications reduces overnight micro-arousals but leaves the device within reach, preserving the mere-presence effect Ward et al. 2017 and the temptation to check during pre-sleep and on waking. (3) "I just use it to read." Chang et al.'s eReader study controlled for content and isolated the device effect: the screen itself was sufficient to delay melatonin and degrade next-morning alertness Chang et al. 2015. Reading on the phone is not equivalent to reading a book.

A fourth misconception worth flagging: the intervention is sometimes characterised as "digital minimalism" or "phone addiction" framing — an asceticism judgement. The mechanistic case stands independently of any moral position on phone use; this is a sleep-and-circadian-physiology intervention.

stakes

Stakes are the felt experience of continuing the typical pattern: phone within arm's reach, last action of the night and first action of the morning. Anchored on the representative reader (a working adult sleeping 6–7 hours nightly with a smartphone on the nightstand), the literature predicts: chronically delayed sleep onset of 10–30 minutes Chang et al. 2015 Exelmans & Van den Bulck 2016; total sleep time shortened by 20–40 minutes per night; degraded next-morning alertness for up to several hours Chang et al. 2015; depleted self-regulation the following workday Lanaj et al. 2014; an elevated baseline anxiety profile from front-loaded morning information; and over months/years the well-documented downstream effects of chronic short sleep on mood, metabolic health, and immune function Walker 2017.

payoff

Onset latency improvements appear within the first week of consistent practice and are often the first thing reported. He and colleagues' RCT showed sleep-quality and affective improvements at four weeks He et al. 2020; observational and clinical reports suggest most of the felt benefit consolidates within one to three months as the bedtime routine becomes habitual. Morning-side effects (reduced first-hour reactivity, smoother CAR profile, higher subjective control over the day) are typically reported faster than night-side effects because the absence of the phone restructures the first-hour behaviourally rather than depending on circadian adaptation.

practicalities

The intervention requires a one-time purchase of a standalone alarm or a dawn-simulation lamp ($15–$200; Lumie Bodyclock, Philips SmartSleep, Hatch Restore are the commonly cited options, with cheap battery-powered analog clocks adequate for the basic case). Operational cost is zero. The friction is behavioural: most adults built the habit of phone-as-alarm and phone-as-last-thing-of-the-night over years, and unwinding it takes ~2 weeks of deliberate setup before it becomes self-sustaining. Practical levers that reduce friction: a charger in the kitchen or hallway; a physical book at the bedside; a partner aligned on the same rule; for the first-hour discipline, a written morning sequence that takes the place of phone-scrolling.

failure-modes

The common pattern of failure is half-measures: phone in the bedroom on do-not-disturb, or under the pillow, or used as the alarm only. These compromise the intervention on both mechanisms (mere presence remains; first-touch on waking is the alarm dismissal). A second failure mode is replacing one input with another: tablet, e-reader, laptop — if it has a screen and a network connection, the same mechanism applies. A third is "I'll just check it for the alarm" — phone-as-alarm is the gateway that erodes the rule. The structural fix is to make checking impossible: phone out of reach, no override.

alternatives

Adjacent interventions partially address the same mechanisms. Dim warm light in the evening (rather than full removal) is documented to reduce melatonin suppression Gooley et al. 2011 but does not address the cognitive-arousal arm. A consistent wind-down routine (any non-screen pre-sleep activity) targets pre-sleep arousal without acting on light. Morning sunlight exposure addresses the CAR and circadian-entrainment side. None of these alternatives is strictly equivalent to phone-free bedroom; in practice they stack rather than substitute.

The credibility range

The optimist case. Multiple mechanisms converge on the same prediction. The melatonin-suppression pathway is mechanistically settled and dose-quantified in humans Gooley et al. 2011 Chang et al. 2015. The mere-presence cognitive effect is replicated Ward et al. 2017. Observational evidence in adults and adolescents consistently shows the predicted direction and magnitude Exelmans & Van den Bulck 2016 Hale & Guan 2015 Carter et al. 2016. One adult RCT produced the predicted improvements He et al. 2020. The intervention is free or very low cost, has no plausible mechanism of harm, and is endorsed by the relevant clinical body AASM 2017. The dawn-simulation morning component has independent RCT support Gabel et al. 2013 Thompson et al. 2014. The package is a high-leverage, low-cost behaviour change with converging mechanistic and observational backing.

The skeptic case. The full intervention has not been tested as such in a large, long, blinded RCT — and arguably cannot be blinded. The cleanest causal evidence (Chang 2015, He 2020) is small-sample and short-duration. The observational adult literature is correlational; reverse causation (poor sleepers reach for phones more) is supported by the same data Exelmans & Van den Bulck 2016. The adolescent literature, while denser, generalises imperfectly to adults whose sleep architecture and phone-use patterns differ. The CAR pathway is mechanistic inference, not a tested causal chain. The intervention is bundled (light + content + first-hour) and decomposing which component does the work is empirically open. The likely true effect on a representative adult is real but smaller than the most-enthusiastic popular framings suggest — closer to 15–30 minutes of total sleep recovered with consistent practice than the "transformative" claims circulating online.

The author's call. The intervention is genuine and high-leverage but the public discourse over-claims it. The defensible call is: clear net positive for sleep onset, total sleep time, and first-hour quality of life, with effect sizes in the moderate range and onset within weeks. Evidence rating earns a 3 (small RCT support, robust mechanism, consistent observational data, clinical-guideline endorsement — held back from 4 by the absence of large adult RCTs on the bundled intervention). Controversy rating is low; this is not a contested topic among sleep medicine specialists, only one whose strongest claims occasionally outrun its trial base.

Stakeholder and incentive map

Pushing the intervention: sleep medicine specialists and the AASM; dawn-simulation lamp manufacturers (Lumie, Philips); the digital-minimalism / attention-protection commentator class (Newport, Haidt); circadian-rhythm researchers who run the underlying mechanistic studies.
Counter-pushing: the attention-economy infrastructure (Apple, Google, Meta, TikTok) whose business model depends on bedside and morning device engagement. They publish "digital wellbeing" features (Screen Time, Digital Wellbeing) that nominally support the user but in practice are easy to bypass and preserve device proximity.
Mixed: smartphone manufacturers ship "Bedtime Mode" features that retain the device on the bedside while reducing salience; these are partial mitigations that do not address mere-presence or CAR pathways.
Cultural pull: norms around always-on availability for work and family create real social cost for going phone-free, particularly for parents of young children and on-call professionals.

Population variability

Habitual late-night phone users with sleep complaints — largest expected effect; the substrate is closest to the intervention.
Light sleepers and shift-workers — benefit substantially from the fragmentation component (no overnight notifications, no glow).
Adolescents and young adults — the literature where the signal is largest Hale & Guan 2015 Carter et al. 2016; phone-use intensity tends to be highest here.
Older adults — benefits expected but smaller because baseline phone-use intensity is generally lower; the dawn-simulation morning component may be the larger fraction of the effect.
Anxiety or depression history — the first-hour component is plausibly outsized; protected morning windows reduce reactivity to inbound stressors, though direct trial evidence is sparse.
Low-baseline-use individuals — small effect; the intervention's effect scales with what is being removed.
On-call professionals and primary caregivers — need a documented bypass for true emergencies; the room-adjacent variant (phone audible from a hallway charger) usually accommodates this without compromising the mechanism.

Knowledge gaps

No large, long-duration RCT of the bundled phone-free-bedroom intervention in a representative adult population with hard sleep endpoints (polysomnography, actigraphy).
Component decomposition unresolved: how much of the effect is light-driven, mere-presence-driven, fragmentation-driven, or first-hour-driven?
Direct evidence on phone-checking and the cortisol awakening response is sparse. The mechanistic story is plausible; the causal trial is missing.
Dose-response for first-hour deferral specifically (30 vs 60 vs 120 minutes) is uncharacterised.
Long-term adherence data is missing; most observational and trial work spans weeks, not years.
The hierarchy between phone-free bedroom and adjacent interventions (dim warm evening light, consistent wind-down, morning sunlight) is not empirically settled. In practice they stack; whether the phone-free piece is the dominant lever or one of several roughly equal levers is open.

Scope and narrowing relative to brief. Brief named six consequences (sleep onset latency, sleep duration, evening light exposure, morning cortisol response, first-hour intentionality, bedtime routine consistency). All six are covered: latency and duration in evidence + stakes + payoff; evening light and the routine in mechanism + protocol; first-hour intentionality across mechanism + payoff. The cortisol awakening response (CAR) is covered mechanistically in the mechanism section but framed honestly: there is no direct human trial of phone-checking versus deferral on CAR amplitude. The article does not over-claim a tested causal chain; the dossier flags it as a knowledge gap.

Category call. Sleep over technology. The dominant consequence cluster is sleep architecture, melatonin onset, sleep duration, daytime energy. Technology & Attention would have been defensible — the substance is technological — but the catalogue category ID is most useful when it tracks where the effect lands, not where the substance lives.

Rating difficulties.

Evidence (3 vs 4). Held at 3. The bundled intervention has not been tested in a large adult RCT; the case rests on a single small RCT (He 2020), convergent mechanism studies, and a denser adolescent literature. 4 would require either a large adult trial or multiple independent small-trial replications.
Sleep (4 vs 5). Held at 4. A 5 would require dominant effect on sleep architecture, which the data don't show for adults specifically — the effect is substantial and reliable but not architecture-redefining at the level of, say, CPAP for apnea.
Mood (3). The CAR mechanism would support a stronger pitch but is not directly trialled; held at 3 based on the affective improvements in He 2020 and the sleep-mediated pathway.
Effort burden (2 vs 3). Honest call: for habitual users the first two weeks feel like willpower, but the steady-state effort is near zero — the structural design of the intervention removes the daily decision. 2 reflects steady state honestly.

Excluded deliberately.

Children and adolescents. The literature is denser there but the parental-control protocol differs enough to warrant its own entry.
Phone-use intensity generally / digital minimalism framing. Out of scope — this entry is sleep-and-circadian, not a position on phone culture.
Specific dawn-lamp product comparisons. Brief mention only. A standalone dawn simulation alarm entry would carry the product-comparison detail.

Future-link candidates. morning-sunlight, evening-light-reduction, wind-down-routine, sleep-debt, dawn-simulation-alarm, screen-time-adolescents. The article's out-of-scope section already gestures at the first four in plain prose; once those entries exist, the renderer can wire them.

Separate-entry candidates surfaced. Cortisol awakening response as its own physiology / measurement entry is borderline — it shows up across several adjacent entries (this one, morning sunlight, NSDR, shift work) and might warrant a shared explainer.