How many tiny LEDs are glowing in your bedroom right now? I’ll go first. I’ve got a charger by the bed, a standby light on the TV, a street-lamp sneaking through my window curtains, a portable fan charger hanging beside my baby’s crib.. and the list goes on and on.

A new mega-study (YES, mega) suggests that faint night-time glow could push our brains toward depression. And if you’re skeptical, just know that this is based on the data of more than half a million people.

Let’s dive in.

Key Findings

Researchers from the University of Barcelona and ten other centres analysed 19 studies spanning more than 550,000 participants into the first ever, full meta-analysis of “light at night” (LAN) and mental health. They compared people exposed to brighter nights (measured by bedside light sensors, wrist trackers or satellite imagery), to those who slept in darker conditions.

The authors mentioned several underlying reasons behind the association between LAN exposure toward the listed outcomes above. Let me share a few interesting ones:

1. One cohort in the study found that low‑level systemic inflammation partly mediated the link between bedroom LAN and new‑onset depressive symptoms in young adults.

2. The daily flow of serotonin, dopamine and other mood‑shaping chemicals is timed to light cues. Circadian mis‑alignment disturbs that rhythm, which results to emotional imbalance .

3. A broken body clock can keep the HPA axis (our “stress gearbox”) high. This raises cortisol levels, and frequently high cortisol levels = anxiety.

4. EVEN night-light levels under 3 lux, which is about the brightness of a hall light leaking under the door, have shown to disrupt the participants’ circadian rhythms!

All in all, it was suggested that LAN “disrupts the circadian rhythm by altering the natural light‑dark cycle” , which then delays melatonin release and disrupts our ability to deep sleep.

What this means for us

• Monitor your phone’s lux meter. Before bed, switch on your phone’s lux‑meter app. If the screen reads above 5 lx when the room lights are off, hunt down the source (standby LEDs, gaps in blinds, etc.) and dim or mask them. Or even better, sell them if you don’t use them anymore.

• Be mindful of the bedside lamp. Swap bedside LEDs for warm‑white (<2700 K) or use cheap orange bug lights.

• Curfew your screen time. For reference, tablets at half‑brightness can produce >30 lx at 40 cm. Implement a no‑screens‑after‑10 p.m. rule or something similar.

• Block the street lamp. Black‑out curtains cut outdoor LAN by up to 90 % (I think there are even some out there that blocks 100%).

I dare you.

If you’ve reached this part, it means you are ready for a quick challenge. Starting tonight, download a lux-meter app on your phone and scan your room. If it reads >7lx, fiercely hunt down that glow, cover it, and re-scan.

Prove the results of this study yourself by keeping a quick journal to keep track of the time it takes for you to fall asleep and how it impacts your mood on waking.

Talk soon,

Krish