Some science behind the scenes

Light therapy

Light therapy—or phototherapy, classically referred to as heliotherapy—consists of exposure to daylight or to specific wavelengths of light using polychromatic polarised light, lasers, light-emitting diodes, fluorescent lamps, dichroic lamps or very bright, full-spectrum light. The light is administered for a prescribed amount of time and, in some cases, at a specific time of day.

Light therapy which strikes the retina of the eyes is used to treat diabetic retinopathy and also circadian rhythm disorders.

Different forms of light therapy are available, and have shown varying degrees of beneficial effect depending on  the pathogen or problem causing the problems:

  • natural sunlight,
  • narrowband (NB)-UVB,
  • broadband (BB)-UVB,
  • UVA,
  • UVA1,
  • cold-light UVA1,
  • UVA and UVB (UVAB),
  • full-spectrum light (including UVA, infrared and visible light),
  • saltwater bath plus UVB (balneophototherapy),
  • Goeckerman therapy (coal tar plus UVB radiation),

and other forms of phototherapy.

Skin diseases

One common use of the therapy is in the treatment of skin disorders, chiefly psoriasis, acne vulgaris, eczema and neonatal jaundice.  But Phototherapy has also been used in the treatment of cutaneous T-cell lymphoma (CTCL). Currently, a number of light sources are available, and selection of the specific modality is based on a number of factors, the most important of which is disease stage.

  • broadband ultraviolet B (UVB) is limited to the patch stage, 
  • ultraviolet A (PUVA) is capable of clearing plaques and, sometimes, early tumors.
  • Narrowband UVB is effective for early stages and has practical advantages over PUVA.
  • Long-wave ultraviolet A (UVA1) has likewise shown efficacy

Long-term remissions have been reported for PUVA, but in the majority of cases, maintenance therapy was necessary. [PMID: 14686973]

Mental illnesses

Light therapy has also been used for a number of mental illnesses:

  •  SAD - light therapy has been the subject of an intensive 25-year research focus on seasonal affective disorder (SAD). Dosing and timing strategies have been honed to optimize the antidepressant effect, and efficacy relative to placebo has provided the evidence base for widespread implementation.
  • Depression - Recent promising initiatives have extended the use of light treatment for non-seasonal major depressive disorder and bipolar depression.  “With light therapy, patients with antepartum depression may find an alternative to medication during pregnancy”.
  • ADHD - Cognitive improvement under light therapy has been noted in adult attention deficit hyperactivity disorder.
  • Parkinson’s - Motor function in Parkinson's disease has improved with light therapy.
  • Dementia - The rest-activity disturbance of elderly dementia has been partially allayed under light therapy.

 

 

References

"Treating psoriasis: light therapy and phototherapy – National Psoriasis Foundation". Psoriasis.org. 2014-02-14.

Sleep Med Rev. 2007 Dec;11(6):497-507. Epub 2007 Oct 25.  Evolving applications of light therapy.  Terman M.

Observations

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