Individual Differences in Melatonin Suppression between Seasonal Affective Disorder Patients and Healthy Controls

Knapen, S. (Stefan) (2013) Individual Differences in Melatonin Suppression between Seasonal Affective Disorder Patients and Healthy Controls. thesis, Medicine.

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Abstract

Seasonal Affective Disorder (SAD) is characterized by recurrent episodes of major depression occurring with a seasonal pattern. Prevalence is around 2-10% in western countries. Light therapy (LT) is the treatment of choice and is highly effective, although the mechanisms behind LT are not clear. Depression is linked to decreased serotonin levels, which is a neurotransmitter hypothesized to be involved in depressive disorders. Light during the day increases serotonin production. This would suggest SAD patients are not sensitive to light, but the opposite is true, the reaction as measured by melatonin suppression in night is supersensitive. The reason for the supersensitivity could be explained by a lower cellular excitability, the need for a stronger signal for the same cellular output. As light is inhibitory to melatonin at night, but stimulatory for serotonin during the day, the lower cellular excitability hypothesis could explain why light therapy works for SAD patients. As intracellular pathways are the same in different cells in the body, this study aims to link the individual characteristics in intracellular pathways of skin fibroblasts to the sensitivity to light as measured by the melatonin suppression by night. This report looks at the melatonin suppression alone. Seven SAD patients and seven healthy control subjects are included in this study. Subjects come included prior to LT and asked for skin biopsies to assess intracellular pathways. They come into the research facility prior to LT. Melatonin values are assessed through saliva sampling from the moment of Habitual Sleep Onset (HSO) until five hours after, every half an hour, in dim light. After one and a half hour subjects are asked to take place in front of a lamp (200 lux) for one and a half hour. Afterwards, the light is set to dim again. Melatonin values are analyzed. One patient was excluded from this study, together with the matched control. SAD patients have significant lower baseline melatonin values (mean ± s.e.m. SAD patients; 13.5 ± 2.5, healthy controls; 26.8 ± 5.3, one-way ANOVA, F(1,10) = 5.2, p = 0.046). No significant melatonin suppression in SAD patients was observed (3.3 ± 1.4, t(5) = 2.4, p = 0.061), neither in healthy controls (12.0 ± 4.9, t(5) = 2.4, p = 0.059). The lower baseline melatonin values in SAD patients are suggestive for lower cellular excitability, it seems SAD patients require a stronger signal from the SCN in order to produce the same amount of melatonin. This hypothesis is not proven by the melatonin suppression at night, because of a limited amount of patients, or because the light duration in the night might not be long enough. Although a strong conclusion is hard to make, this report suggests a lower cellular excitability in SAD patients.

Item Type:	Thesis (Thesis)
Supervisor name:	Werken, Maan van de and Gordijn, Marijke
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 10:41
Last Modified:	25 Jun 2020 10:41
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/299

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