Panic disorder is where a person has recurring and regular panic attacks. In the UK, it affects about two in 100 people, and it's about twice as common in women as it is in men. Previous studies have shown that there is a strong seasonal component in panic disorder, but this is the first study to look specifically at panic disorder patients' reactions to light.

A group of researchers from the University of Siena (Italy) compared 24 patients with panic disorder (PD) against 33 healthy controls. Using a standard Photosensitivity Assessment Questionnaire (PAQ), they found that healthy controls showed a slight (not statistically significant) tendency to be photophilic -- to be attracted to bright light. In contrast, the patients with panic disorder showed medium to high levels of aversion to bright light.

The Photosensitivity Assessment Questionnaire asks subjects to agree or disagree with a series of questions about their attitude towards light, for example "My ideal house has large windows" or "Sunlight is so annoying to me, that I have to wear sunglasses when I go out." The mean values in the Photosensitivity Assessment Questionnaire were as follows: patients with photophobia scored 0.34 (± 0.32 SD), healthy subjects scored 0,11 (± 0,13 SD).

According to lead researcher, Dr Giulia Campinoti: "There have been several hints that photophobia is associated with panic disorder; for example in some people, fluorescent light can induce panic attacks. It had also been noted that people with panic disorder often protect themselves from light, for example by wearing sunglasses.

We believe that photophobia is one of the elements which may increase the risk of people suffering from panic attacks, but this is a small study, so it needs to be confirmed by a longer-term follow-up trial. For example, we need to understand if the photosensitivity and panic attacks continue to be related over time. If we can confirm this, then we may be able to take steps to avoid some of the triggers to panic attacks. It is important to note that our work shows an association, not necessarily a cause and effect. We don't yet know exactly what the relationship might be, but there is probably some underlying biochemical basis."

Commenting for the ECNP, Professor Siegfried Kasper (Vienna) said: "This is a very interesting study that confirms our previous finding that anxiety components within depression cannot be treated with light therapy."

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Materials provided by European College of Neuropsychopharmacology (ECNP). Note: Content may be edited for style and length.