Blood serotonin, serum melatonin and light therapy in healthy subjects and in patients with nonseasonal depression

Abstract

The 24-h rhythms of blood serotonin and serum melatonin were determined in 39 unmediated inpatients with nonseasonal affective disorder and in 14 healthy men and women after 7 days of morning bright-light (2500 lx) or dim-light (50 lx) treatment. Bright-light treatment led to a more than 50% decrease in the Hamilton Rating Scale for Depression (HRSD) score in 4/19 patients and dim light in 1/17 patients. After light treatment the mesor (the daily mean estimated by cosinor analysis) of patients' and subjects' melatonin levels did not change significantly, nor was there a correlation between phase change and decrease in HRSD score. We observed after bright- and dim-light treatment a consistent increase in blood serotonin in patients and healthy subjects, which differed significantly between healthy subjects and patients. These findings suggest the involvement of serotonergic mechanisms following light therapy.

Testing the Hypothesis of a Circadian Phase Disturbance Underlying Depressive Mood in Nonseasonal Depression

“…This small group size raises the possibility of insufficient power to detect differences. The strong point of the present study is that it is a within-subjects comparison, in contrast to the between-subjects comparison of two other studies that examined clinical change in relation to chronobiological variables (Rao et al, 1992;Yamada et al, 1995). In this context, the present study might play a role in the discussion on the possible pathogenetic role of circadian phase disturbances in depression.…”

“…The result that opposite phase shifts within the same subject do not result in opposite mood changes strengthens the conclusion that no clear relationship between shifts of the circadian system and mood exists in the present group of depressives and healthy subjects. This is the third study that concludes that the possible effects of light in nonseasonal depressives are not mediated by chronobiological mechanisms (Rao et al, 1992;Yamada et al 1995). Alternative explanations for the lack of a mood change in the present study are that the phase shifts induced were too small to obtain effects or that the duration of the shifts did not last long enough.…”

“…In three studies, the effects of controlled light exposure on the depressive symptomatology in relation to shifts in circadian rhythms were tested. With the exception of the case study by Lewy et al (1985), the two recent large studies by Rao et al (1992) and Yamada et al (1995) provided no evidence for a relationship between clinical change and chronobiological variables. This conclusion was based on comparisons between groups of patients, not selected for possible predicting characteristics.…”

“…In the course of our study, it became clear that the overall responses of our nonseasonal depressed patients to the short-lasting light conditions were clinically negligible. Moreover, data were being published suggesting that in those cases in which nonseasonal depressives were reported to benefit from light therapy, longer periods of treatment were used (Kripke et al, 1992;Rao et al, 1992;Wetterberg, 1992). For those reasons, we limited the study to 8 patients.…”

A systematic review of light therapy on mood scores in major depressive disorder: light specification, dose, timing and delivery

“…The comprehensive analysis also suggests that light therapy can improve melatonin amplitude and cyclical sleep patterns along with improvement in depression score [29]. There are currently no guidelines to determine which patients will benefit from light therapy, as a few studies have demonstrated no impact of light therapy on patients with NSAD [20,21,[30][31][32]. Furthermore, there has been no systematic evaluation and synthesis of the published literature regarding characteristics (colour, intensity), exposure dose (duration and timing) and the mode of delivery (light boxes, visor etc) of light for use as a treatment for NSAD patients.…”