The Science of Negative Air Ionization

vacuum cleanerWhat are negative air ions, and how do they affect us?

When a tiny electron hitches a ride on an oxygen molecule, giving the oxygen molecule a negative charge, a negative air ion is born. The negative air ion continues to carry the electron, and hence a negative charge, when water molecules surround it, and keep the electron and the molecule bound together.

Negative air ions attract dust, pollen, bacteria, viruses, and other undesirable particles. When they do so, the resulting combination is then too heavy to remain floating around. Such heavy clumps of ions and particles thus drop to the ground, leaving the air fresh, and clean.

A negative air ionizer, then, is like a natural, miniature vacuum cleaner that purifies the air.

However, negative air ions also serve another function – one potentially more important, and one you may have already experienced. Negative air ions, especially in large quantities, can make people feel better, and even reduce depression. That may be why, when you are in a place with high concentrations of negative air ions, such as a beach, or waterfall, or meadow, you feel better.


Drawing for CET by Theresa Desrochers © 2018 |

Our city homes and offices tend to have fewer negative air ions because radiators and air conditioners dry out the air. Without moisture in the air, water molecules cannot surround an oxygen molecule, and ensure that the extra electron – with its negative charge – stays with it. For that reason, city dwellers sometimes buy negative air ionizers.

Here, however, we will focus on the scientific literature on negative air ionization, and its affect on mood. While we are not sure how these particles affect us, there is a solid body of literature showing that high concentrations of negative air ions have a positive effect on mood. We present the details below in the form of summaries of key articles. PDFs of each article are available for those who would like to dig deeper.

Treatment of Seasonal Affective Disorder with a High-Output Negative Ionizer

Seasonal Affective Disorder (SAD), sometimes known as winter blues, is often characterized by:

  • oversleeping
  • overeating
  • fatigue.  

To treat these symptoms, subjects were exposed to ion treatment at home for 30 minutes each morning for 20 days. Far more of the subjects exposed to high density (vs low density) ion treatment recovered (58% vs 15%).  Further, when the ion treatment was stopped, all the subjects who recovered became depressed again.

The effectiveness of the high density ion treatment, and the absence of side effects, suggest that this therapy would be effective alone, or as a supplement to other treatments for seasonal affective disorder.

Controlled trial evaluation of exposure duration to negative air ions for the treatment of seasonal affective disorder

This study confirmed the results of the research just described. Specifically, subjects with seasonal affective disorder were far more likely to get better when exposed to 18 days of sessions with high density negative air ions compared with a placebo (no negative air ions).

Further, the subjects got better regardless of whether they had 30-minute, or 60-minute, sessions.

Finally, people who received an ion treatment were more likely to get better if they had a morning (vs evening) chronotype (that is, were early birds vs night owls). However, as other research confirms, people with either kind of chronotype improved with ion treatment.

IONS PAGE – sidebar – owl bird worm FINAL
Controlled trial of bright light and negative air ions for chronic depression

Both high density negative air ion therapy, and bright light therapy, known more commonly as light therapy, are effective for seasonal affective disorder. This experiment showed that both treatments worked for chronic depression, too.

In this study, subjects were randomly assigned to have either bright light therapy, or high density negative air ion therapy, or low density negative air ion therapy. The first two groups both showed significant improvements in mood. Further, half the subjects in each group overcame their depression.

In contrast, the low ionization group only showed some improvement in mood, and no one in that group completely got over his or her depression.

These results are important because they show that the effectiveness of two non-pharmacologic treatments is not limited to seasonal forms of depression, but works for more serious forms of depression, too. Therefore, these two treatments may be added to other therapies, or vice versa, to improve results for patients with major depression.

Bright light, negative air ions and auditory stimuli produce rapid mood changes in a student population: a placebo-controlled study

Music, bright light, and high-density ions were all equally effective in quickly improving mood in young adults. Student subjects included a subset with symptoms of depression.

Controlled Trial of Naturalistic Dawn Simulation and Negative Air Ionization for Seasonal Affective Disorder

light box

Drawing for CET by Theresa Desrochers © 2018 |

Subjects were given one of five treatments. The first four (vs the last) were closely matched in the substantial extent to which they reduced seasonal depression

Specifically, each treatment reduced depression in the following percentages of people who had that treatment:

  • bright light, 57%
  • a simulation of sunrise (dawn simulation) timed to wake the patient up naturalistically, 50%
  • dawn pulse (thirteen minutes of light matched to the dawn simulation), 43%
  • high-density negative air ions, 48%
  • low-density negative air ions, 23%.

These results indicate that treatments, such as dawn simulation and high-density negative air ions, can be effective for depression without the active involvement of a depressed patient.

Air ions and mood outcomes: a review and meta-analysis

This review covers eighty years of reports on negative air ionization, mostly at low levels, far below those used in more recent studies . It includes tables summarizing studies and their outcomes, as well as a comprehensive meta-analysis (statistical analysis combining the results of multiple studies).

No consistent results were found for the effects of ions on anxiety, sleep, and other variables. However, the effects of ions on depression was more consistent. Specifically:

  • ions, especially high-density ions, were associated with less depression
  • the mood of patients with seasonal affective disorder (SAD) improved substantially in response to  high-density ions, but only negligibly in response to low-density ions
  • the mood of patients with chronic depression only improved with exposure to high-density ions.