Light treatment in seasonal and nonseasonal depression : diagnostic, clinical and neurendocrine studies

There is a need for evaluation of new treatment modalities in depression. The aims of thisthesis were to investigate the effect of 2 hours of daily light treatment for 10 days in patientswith a major depression with seasonal or nonseasonal pattern and to study subgroups ofdepressed patients with respect to clinical, demographic, and neuroendocrine factors, theeffect of exposure to bright light, dexamethasone suppression test, CRH stimulation and thehormonal effect of light exposure on healthy controls. The patients with a seasonal pattern (Seasonal Affective Disorder; SAD, n=99),were less depressed, had higher frequency of carbohydrate craving, increased appetite, anda lower frequency of treatment with drugs, sick leave and hospitalization for depression thanthose with a nonseasonal pattern (n=28). In a sample of 90 patients those with a seasonalpattern (n=68) improved significantly better to treatment with bright light of 350 cd/m2. Nodifferences were found between light treatment in the morning (6-8 a.m.) or in the evening(6-8 p.m.). The treatment effect was not related to the severity of the depression, sex, age,medication or month when the light treatment was given. In 63 matched depressed patients nodifferences were seen before or as a result of light treatment between those with a seasonal(n=42) and nonseasonal (n=21) pattern in the area under curve (AUC) and the phase (TC) ofserum melatonin, mesor and amplitude of serum cortisol, measured at nine time-points duringthe night (8 p.m. - 8 a.m.). The melatonin AUC was significantly reduced by light treatment.Serum melatonin TC was advanced by morning light and delayed by evening light. Basallevels or changes of serum melatonin (AUC and TC) were not related to the therapeuticoutcome. The batyphase of serum cortisol was significantly advanced by morning, but not byevening light. The amplitude and the mesor of serum cortisol were not affected by lighttreatment. A delay in the batyphase of cortisol showed a weak, but significant relation toimprovement of the depression. A cosinor analysis of serum melatonin and cortisol showedthat the batyphase of cortisol occurred approximately three hours earlier than the acrophase ofmelatonin and that 43% of the changes in the melatonin acrophase were reflected by a changein the cortisol batyphase. In a study of 13 healthy volunteers, a 15- minute light exposure in the eveningwas shown to significantly suppress melatonin, but not cortisol. Light exposure at 10 -11 p.m.in the groups of patients with seasonal and nonseasonal depression suppressed melatonin, butnot cortisol. There were no differences between the two groups, and no relationship was foundbetween treatment efficacy and the suppression of melatonin. In 24 patients with major depression, subgrouped in suppressors andnonsuppressors from their DST response to 1 mg of dexamethasone, nonsuppressors showed asignificantly lower ACTH and cortisol responses (AUC) after stimulation with 0.45µgcorticotrophin releasing hormone (CRH). These differences were no accounted for in theseverity of their depression. In summary: Depressed patients with a seasonal pattern improved more thanthose with a nonseasonal pattern to 2 hours of daily light exposure for ten days. Theimprovement was not related to the severity of their depression, morning or evening lighttreatment or hormonal changes in the level or phase of serum melatonin or the amplitude ormesor of serum cortisol.Key words: Depression, seasonal, nonseasonal, light treatment, clinical ratings, melatonin,cortisol, ACTH, CRH, dexamethasone suppression testBj rn-Erik Thalen, 1996Printed in Sweden by Repro Print, Stockholm. ISBN 91-628-2097-