Brief reportMorning sunlight reduces length of hospitalization in bipolar depression
Introduction
The effectiveness of bright light therapy of depression may be not limited to seasonal affective disorder (SAD) (Kripke, 1998). Natural sunlight might share the clinical effects of artificial light. In SAD, natural light in the morning had the same efficacy of artificial light (Wirz-Justice et al., 1996), and severity of depression negatively correlated with photoperiod (Oren et al., 1994). Daily recordings revealed a relationship between mood, hours of sunlight, and solar irradiation in two non-SAD affective patients (Summers and Shur, 1992, Eagles, 1994). Unmonitored light therapy caused marked mood oscillations (Meesters and Van Houwelingen, 1998), and a strict control of the light/dark cycle improved treatment-refractory rapid-cycling bipolar illness (Wehr et al., 1998, Wirz-Justice et al., 1999).
The orientation of rooms in a Canadian ward provided a 'natural experiment' on the relationship between sunlight and length of hospitalization for depression (Beauchemin and Hays, 1996). Patients in sunny rooms had a mean 2.6-day shorter hospitalization than patients in dimly lit rooms, a difference more marked in men (6.8 days) than in women (0.7 days).
Our ward is favourably situated to replicate and expand this naturalistic observation. In a corridor with rooms on either side, windows are oriented to East or West. Eastern rooms (E) receive direct sunlight in the morning, while western rooms (W) receive it in the evening. Ambient light intensity in the two conditions (avoiding direct sunlight, which reached more than 30 000 lux) showed wide differences: on a bright May day at 09:00 h an E room measured at 15 500 lux, and a W room at 1400 lux, while at 17:00 h an E room measured at 2700 lux, and a W room at 3000 lux; on a day with light clouds values were E=1500 lux and W=150 lux at 09:00 h, and E=200 lux and W=1500 lux at 17:00 h; while in a cloudy day values were E=650 lux and W=150 lux at 09:00 h, and E=140 lux and W=600 lux at 17:00 h.
Artificial bright light therapy has an higher efficacy in the morning (Lewy et al., 1998): if sunlight has the same effect, a difference should be detected between E and W conditions.
Section snippets
Method
We reviewed charts for all admissions for non-psychotic depression over a 3-year period (1996-98) with a diagnosis of major depressive disorder, single or recurrent, or bipolar disorder, depressive episode, moderate or severe (DSM IV criteria), without Axis I codiagnosis and with a length of stay longer than 6 days.
Rooms (E or W) had been randomly assigned based on first available free space. Psychiatrists in charge were the same for E and W rooms. Medications were administered upon clinical
Results
Results are summarized in Table 1.
No significant difference was detected in the unipolar group.
In the bipolar group hospitalization was significantly shorter for E rooms in the whole sample. Significant differences were detected for summer and fall admissions.
Discussion
Only bipolar depressed inpatients exposed to natural sunlight in the morning had an hospital stay shorter than patients exposed in the evening, with no gender effects. Given the sex distribution of unipolar and bipolar disorder, it is possible that the previously reported sex differences on the effects of sunlight (Beauchemin and Hays, 1996) could be due to the effect of the unipolar/bipolar dichothomy.
Bipolar patients showed an increased sensitivity to the biological effects of light (Lewy et
Acknowledgments
We thank Dr Anna Wirz-Justice for precious help during manuscript preparation.
References (16)
Summertime bright-light treatment of bipolar major depressive episodes
Biol. Psychiatry
(1993)- et al.
Sunny hospital rooms expedite recovery from severe and refractory depressions
J. Affect. Disord.
(1996) - et al.
Effects of phototherapy on non-seasonal unipolar and bipolar depressive spectrum disorders
J. Affect. Disord.
(1991) The relationship between mood and daily hours of sunlight in rapid cycling bipolar illness
Biol. Psychiatry
(1994)- et al.
Natural bright light exposure in the summer and winter in subjects with and without complaint of seasonal mood variations
Biol. Psychiatry
(1998) Light treatment for nonseasonal depression: speed, efficacy, and combined treatment
J. Affect. Disord.
(1998)- et al.
Manic-depressive patients may be supersensitive to light
Lancet
(1981) - et al.
The relationship between onset of depression and sudden drops in solar irradiation
Biol. Psychiatry
(1992)