Subsensitive melatonin suppression by dim white light: possible biological marker of panic disorder

Abstract

Light is involved in providing entrainment of circadian rhythms and the suppression of the pineal hormone melatonin. In patients with affective disorders, there have been indications of circadian as well as seasonal variation in illness, which may be reflected in melatonin production. Varying sensitivity to light has been noted within healthy individuals as well as in some patients with affective disorders. Recent evidence suggests that patients with panic disorder may have an altered and phase-delayed melatonin rhythm. The present study examined the nocturnal plasma melatonin rhythm in patients with panic disorder, and also examined their melatonin sensitivity to dim light. The melatonin rhythm was examined in 6 patients with panic disorder and 8 controls. The melatonin sensitivity to dim white light (200 lx) was examined in 8 patients with panic disorder and 63 controls and was compared to that of a group of 7 patients with other anxiety disorders. Patients with panic disorder demonstrated a trend towards higher and delayed peak melatonin levels compared to controls. Patients with panic disorder also had a subsensitive melatonin suppression by dim white light, compared to controls and patients with other anxiety disorders (p<0.005). The phase-delayed circadian rhythm observed in patients with panic disorder may be secondary to the subsensitivity of the melatonin response to light. It is hypothesized that the subsensitivity may be due to abnormal neurotransmitter/receptor systems involved in regulation of melatonin suppression and circadian rhythmicity, and may lead to phase- delayed circadian rhythms. The melatonin subsensitivity to light may be used as a biological marker of panic disorder.

Photosensitivity in panic disorder

“…[10] Also, our findings raise the question of what the specific relationship is between light exposure and those neurotransmitters whose imbalance has been linked to mood and anxiety disorder, such as melatonin, [11][12][13] the serotoninergic system, [14,15] or the dopaminergic system. [16][17][18] For instance, it is well known that dopamine synthesis at least in certain specific retinal neurons is rapidly activated by light, [19] and recent findings have suggested a beneficial effect of bright light therapy for Parkinson's disease.…”

Neuroendocrine Regulation of Anxiety: Beyond the Hypothalamic‐Pituitary‐Adrenal Axis

“…Plasma melatonin may be elevated in patients with anxiety disorders, decreasing to normal levels following treatment . In addition, patients with panic disorder have demonstrated melatonin hyporesponsivity, which could result from a persistent hyperelevation . Studies in rodents have shown an anxiolytic effect of melatonin and of its agonist, agomelatine.…”

Changes Caused by the Melatonergic System in Young Patients with Mood Disorders: A Literature Review

“…Abnormal melatonin rhythms have been also reported in patients with mood disorders [6,7]. Several studies have found that patients with bipolar disorderare likely to show abnormal melatonin secretion and increased light-induced melatonin suppression [8][9][10][11]. In major depression, there were inconsistent findings of melatonin secretion or levels compared to healthy subjects [12][13][14][15].…”