Negative Air Ionisation

Our rating
Seasonal affective disorder 1 smiley: This treatment is promising and may be useful. It has some evidence to support it, but more evidence is needed to be sure it works.
General depression Question mark: This treatment has not been properly researched. It is not possible to say whether it is useful or not.


The rating system

  • 3 smiliesThese treatments are very useful. They are strongly supported as effective by scientific evidence.
  • 2 smiliesThese treatments are useful. They are supported by scientific evidence as effective, but the evidence is not as strong.
  • 1 smileyThese treatments are promising and may be useful. They have some evidence to support them, but more evidence is needed to be sure they work.
  • No smiley On the available evidence, these treatments do not seem to be effective.
  • Question markThese treatments have not been properly researched. It is not possible to say whether they are useful or not.
  • Exclamation MarkSafety or other concerns have been raised for the use of these treatments.

What is it?

A negative air ion is an atom or molecule in the air that has gained an electron, while a positive ion has lost an electron. Both positive and negative ions occur naturally in the air. However, negative ions are more concentrated in fresh air. Negative air ions can be produced by lightning, ocean surf and waterfalls. There are also electrical devices called 'air ionisers' that produce negative air ions. Such air ionisers have been used in the treatment of seasonal winter depression, or seasonal affective disorder (SAD). Treatment generally involves sitting in a room with the ioniser on for 30 minutes every morning over a 2-3 week period.

How does it work?

Negative air ionisation is mainly used for people who tend to become depressed in autumn and winter, when the daylight is shorter. These people then get better in spring and summer. This type of depression is known as seasonal affective disorder (SAD). It is unclear how negative air ions might improve mood, and more research is needed to better understand how it might work.

Is it effective?

There have been a number of small studies which have looked at the effects of air ionisation on winter depression. One meta-analysis which looked at the results from five studies found that high density air ionisation was effective at helping people with both SAD and non-seasonal clinical depression, while low density air ionisation was only effective for people with SAD.

Most of the research looking at negative air ionisation for depression has focussed on people with seasonal depression. More research is needed to better understand if negative air ionisation is helpful for people with non-seasonal depression.

Are there any disadvantages?

Some air ionisers produce a very small amount of a gas called ozone, which can be harmful to humans. Air ionisers should be used in a well ventilated room to ensure that ozone levels do not build up to toxic levels.  

Where do you get it?

Air ionisers are available from electronics stores and can be bought on the internet. It is important to check the technical specifications of any air ioniser to see if they produce a high density of negative ions.


Air ionisation appears to be an effective treatment for seasonal winter depression, but it is recommended that other better supported treatments such as light therapy are tried first. More research is needed to understand if air ionisation could be helpful for non-seasonal depression.

Key references

  • Bowers B, Flory R, Ametepe J, Staley L, Patrick A, Carrington H. Controlled trial evaluation of exposure duration to negative air ions for the treatment of seasonal affective disorder. Psychiatry Res. 2018; 259: 7-14.
  • Britigan, N., Alshawa, A., & Nizkorodov, S. A. Quantification of ozone levels in indoor environments generated by ionization and ozonolysis air purifiers. J Air Waste Manag Assoc. 2006; 56(5): 601-610.
  • Flory R, Ametepe J, Bowers B. A randomized, placebo-controlled trial of bright light and high-density negative air ions for treatment of Seasonal Affective Disorder. Psychiatry Res. 2010 May 15; 177(1-2): 101-8.
  • Goel N, Etwaroo GR. Bright light, negative air ions and auditory stimuli produce rapid mood changes in a student population: a placebo-controlled study. Psychological Medicine. 2006; 36(9): 1253-63.
  • Goel N, Terman M, Terman JS, Macchi MM, Stewart JW. Controlled trial of bright light and negative air ions for chronic depression. Psychological Medicine. 2005; 35(7): 945-55.
  • Perez V, Alexander DD, Bailey WH. Air ions and mood outcomes: a review and meta-analysis. BMC Psychiatry. 2013; 13:29.
  • Terman M, Terman JS. Treatment of seasonal affective disorder with high-output negative ionizer. Journal of Alternative and Complementary Medicine 1995; 1: 87-92.
  • Terman M, Terman JS, Ross DC. A controlled trial of timed bright light and negative air ionization for treatment of winter depression. Archives of General Psychiatry 1998; 55: 875-882.

Last reviewed and updated: 27 November 2023