Emerging therapy

Photobiomodulation

Transcranial near-infrared light, low-level laser therapy, PBM

Non-invasive, painless and inexpensive compared with cell therapies — with small, mostly short studies behind it and a wide gap between what is claimed and what has been shown.

Where it stands, condition by condition

The same therapy can be well supported for one problem and completely untested for another. This is the single most common place families are misled.

What it is

Photobiomodulation applies red or near-infrared light to the scalp — usually in the 600–1100 nanometre range — through LEDs or a low-power laser. It does not heat tissue and it is not the same as the lasers used in surgery.

Sessions typically last several minutes and are repeated over weeks. Home-use helmets and headbands are sold directly to families.

The treatment is easy to deliver, which is part of the problem: ease of use has let marketing move far ahead of evidence.

How it is meant to work

Light at these wavelengths is absorbed by cytochrome c oxidase, an enzyme in the mitochondria, which may increase cellular energy production and reduce oxidative stress.

Secondary effects on blood flow and inflammatory signalling have been described.

How much light actually reaches the brain through scalp and skull is contested, and it differs between a small child and an adult. Dose at the scalp is not dose at the cortex.

What has actually been tested

• In autism, small randomised and sham-controlled studies have reported improvements on behaviour rating scales after several weeks of transcranial near-infrared treatment.
• These are promising but preliminary: tens of participants rather than hundreds, short follow-up, and different devices, wavelengths and schedules between studies, which makes results hard to combine.
• Rating scales filled in by parents who know whether the device was switched on are vulnerable to expectation. Sham-controlled design helps, and the better studies use it.
• Most transcranial photobiomodulation research overall has been done in adults, particularly after traumatic brain injury. Adult results do not transfer automatically to a developing brain.

What we still do not know

• The right dose, wavelength and schedule — current protocols are not standardised.
• Whether reported behavioural gains last beyond the treatment period.
• Whether home devices deliver what clinic devices deliver.
• Whether any effect is specific, or reflects the attention and routine that come with daily sessions.

Risks and costs

• Direct harm appears uncommon; reported effects are usually mild and short-lived, such as headache, warmth or irritability.
• Eye exposure must be avoided, particularly with laser devices.
• The realistic harm is opportunity cost: money and daily time spent on this instead of therapies with stronger evidence.

Questions to ask before you agree

1. Which device, wavelength and session length, and which published study used that exact protocol?
2. Was the study sham-controlled?
3. How will we decide, at a set date, whether this is working — and what stops it if it is not?

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