New SAD Treatment
The winter season sometimes comes along with depression and lack of energy and this is called seasonal-affective disorder (SAD). It is thought that the reason why people develop this disorder is shortage of natural light and so the obvious treatment for these patients is light therapy. This consists of exposing the patient to a bright, full-spectrum light at certain times of the day. The effectiveness and exact mechanism of this light-treatment was not fully understood until now, until researchers from Oulu, Finland, found that the central role was not played by the retina. Instead the light acts on light-sensitive proteins on the brain’s surface. Special earphones were designed that shine a beam of light through the ear canal to a light-sensitive area in the brain, this being an efficient alternative to light therapy.
Juuso Nissilä, a physiologist at Oulu University, found that 18 separate regions of the brain express opsin-3, a light-sensitive protein that is also found in the human retina. There regions include areas that are involved in the production and storage of neurotransmitters like melatonin (which plays an important role in sleep activity) and serotonin and dopamine. The light-sensitive proteins in these areas may have a greater impact on the mood than proteins normally found in the retina. Nissilä considers that during daylight these proteins react to light transmitted through the skull: “Bone is actually quite a good transmitter of light – put a torch inside a skull and you’ll see the beam very clearly – so I now think that it’s the light reaching your brain surface through your skull which is the important factor.”
Fortunately, these areas in the brain can be easily reached through the ear canal so they can be used as an efficient alternative to classic light therapy. Nissilä adds that ”Shining light into the brain through the ears is a far better way to deliver bright light therapy than staring at a lamp. There are two good reasons to use the ears. The first is that the skull is thin around the ear canal area, and a very good proportion of the light gets through. The second is that there are comparatively few blood vessels on the surface of the brain at that point.” The earphones he developed contain a white LED that produces wavelengths close to that of the sun.
The results from the first clinical trial were published in the journal Medical Hypothesis. During four weeks, patients wore earphones that were shining 6.0-8.5 lumen bright light into their ear canals for 8-12 minutes every day, then they were given two questionnaires. According to the data collected from a self-rated questionnaire, designed for psychological study, 92% of the patients with SAD achieved full remission, while the data collected from a psychiatrist-rated questionnaire showed that the therapy was effective on 77% of patients. In the near future, the researchers plan to investigate the earphone therapy with randomized placebo-controlled and dose-finding study designs.