تاثیر چرت زدن در طول روز در مقابل فعالیت کنترل شده بر روی بهزیستن ذهنی بیماران مبتلا به افسردگی اساسی

Abstract While the impact of sleep on cognitive functions such as memory is under extensive study, the role of sleep in modulating a persons' subjective well-being remains largely uncharacterized, especially in groups with psychiatric disorders. To gather more information on this topic a study was conducted with 20 patients suffering from Major Depression (MD) and 20 healthy controls, matched for age, gender and education. All subjects rated their subjective well-being at 10 a.m. in the morning. Half of the subjects in each experimental group were given the opportunity to nap in the afternoon between 2 p.m. and 3.30 p.m., while the other half stayed awake accompanied by controlled activity. All subjects rated their subjective well-being again at 4 p.m. Only the group of patients with MD who were given the opportunity to sleep during the day showed a significant improvement in subjective well-being from morning to afternoon. All the other subgroups showed no significant changes across the time interval. The results of this study suggest that depressive patients benefit from daytime naps with regard to their subjective well-being. Further research is needed to determine the exact mechanisms of this improvement.

Introduction There are several studies reporting positive effects of daytime napping on different cognitive functions in healthy adults. For example, a positive influence of napping on processes of memory consolidation has been reported and is one of the main topics currently discussed in the field of sleep research (Backhaus and Junghanns, 2006, Lahl et al., 2008 and Nishida et al., 2008). Sleep can be divided into different stages, with each sleep stage being defined by specific characteristics, for details see the American Academy of Sleep Medicine (AASM) manual for the scoring of sleep (Iber et al., 2007). Rapid eye movement (REM) sleep is characterized by high-frequency, low-voltage EEG activity and bursts of rapid eye movements of the eye muscles, coupled with atonia of major skeletal muscles. NonREM (NREM) sleep stages include stage 1 (the lightest stage of sleep), stage 2 (defined by the emergence of K-complexes and sleep spindles) and slow-wave-sleep (SWS) (characterized by increased delta activity). During a short phase of daytime sleep different stages of the sleep cycle can be reached, including REM sleep (Dhand and Sohal, 2006). Daytime sleepiness and nodding off often occur between 2:00 p.m. and 4:00 p.m. (Dinges, 1989 and Dinges, 1992). Naps with a duration between 10 and 45 min were found to have restorative effects for healthy young and elderly adults (Dhand and Sohal, 2006). Very few studies on sleep and memory consolidation have been conducted in patients with psychiatric disorders. Investigations are scarce due to the great heterogeneity of the patient groups and the great number of confounding aspects like medication, comorbidities or drug intake typical of these populations (Diekelmann et al., 2009). The results reported from studies in patients with psychiatric disorders suggest a relationship between disorder specific sleep patterns and memory performance for patients with schizophrenia or major depression (Göder et al., 2004, Göder et al., 2007, Hornung et al., 2008, McNamara et al., 2009 and Seeck-Hirschner et al., 2009). Other psychological aspects, such as a person's mood, have been reported to benefit from a 20 to 30-min daytime nap in healthy young adults (Taub et al., 1976 and Kaida et al., 2007). Subjective well-being seems to be modulated by specific sleep factors such as sleep pressure and circadian phase (Birchler-Pedross et al., 2009). Patients with Major Depression (MD) show abnormal sleep characteristics like reduced SWS and a higher amount of REM sleep as well as shorter REM latencies and higher REM densities (Riemann et al., 2001). Moreover, decreased sleep efficiency is typical of MD patients, defined by difficulties falling asleep, nocturnal awakenings, and early-morning awakenings (Thase, 2006). There is some evidence for a relationship between excessive daytime sleepiness and depressive symptoms, indicating that daytime sleepiness is a regular feature of depression (Fava, 2004, Lessov-Schlaggar et al., 2008 and Mume, 2010). A large amount of research has focused on the influence of sleep deprivation (SD) as a therapeutic option for this group of patients (Riemann et al., 1995 and Giedke and Schwärzler, 2002). Today a positive influence of SD is assumed, although no comprehensive explanation for the phenomenon is known (Svestka, 2008). Furthermore, the high risk of a relapse limits the use of SD as a long term therapy (Martiny et al., 2007). Studies which investigated the influence of naps on the efficiency of SD in MD patients reported heterogeneous results (Gillin et al., 1989, Wiegand et al., 1993 and Hemmeter et al., 1998). Wiegand et al. (1993) reported that depressed patients having responded to total sleep deprivation therapy relapsed more frequently into depression after morning naps compared to afternoon naps. In contrast, Gillin et al. (1989) looked at the effects of 10-min naps scheduled either at 8:30 a.m. or at 3:00 p.m. on mood in sleep-deprived depressed patients. They found that naps did not alter mood in the responders to total sleep deprivation, but did improve measured depression on the Hamilton Rating Scale for Depression in the non-responders (Gillin et al., 1989). It seems likely that, based on circadian changes in MD, the time when the nap takes place (in the morning versus in the afternoon) is an important determinant of the outcome of the SD treatment. In sum, a strong relationship between sleep, sleep alterations and depressive symptoms is assumed in MD (Riemann et al., 2001 and Tsuno et al., 2005). Most of the napping studies in MD have concentrated on patients who were sleep deprived. There is a lack of information on the relationship between daytime sleep and subjective well-being in patients suffering from MD who are not sleep deprived. To our knowledge, no study has been published yet exploring this topic outside the scope of a SD paradigm. In contrast, there are some therapeutic concepts that focus on behavioral activation treatments and report an improvement in depressive symptoms after resuming activity (Cuijpers et al., 2007 and Hautzinger, 2008). Following this idea, taking a nap would be a dysfunctional intervention for treating a patient with depression. The present study was part of a research project focusing on the effects of napping on emotional memory consolidation and subjective well-being in patients with MD. Based on prior findings with regard to the positive effect of daytime sleep on mood in healthy adults (Taub et al., 1976 and Kaida et al., 2007) it was hypothesized that healthy controls who slept during the day would show an improvement in their subjective well-being in comparison to controls who stayed awake. For the clinical group, it was expected that MD patients who took a nap would show a worsening in their subjective well-being compared to patients who did not sleep during the day. This hypothesis takes into account the marked changes in sleep architecture typically observed in depressed patients (Riemann et al., 2001 and Thase, 2006) and the findings from studies investigating the effects of a nap within a SD paradigm (Gillin et al., 1989, Wiegand et al., 1993 and Hemmeter et al., 1998). Moreover, the hypothesis is based on findings within psychotherapy research showing a positive correlation between activation during the day and a reduction in depressive symptoms (Cuijpers et al., 2007 and Hautzinger, 2008).

Results The ANOVA showed a significant main effect of time (F(1,36)=6.827, p=0.013) for the tests of within-subjects contrasts. Also the interaction for time×group (F(1,36)=17.718, p=<0.001) and for time×condition (F(1,36)=5.963, p=0.020) was statistically significant. The interaction time×group×condition was not significant (F(1,36)=1.322, p=0.258). Testing the significant interactions revealed different patterns for the interaction between sleep and subjective well-being in patients with MD compared to healthy controls. The pre-ratings in both conditions (sleep versus active) showed no significant differences, neither for the MD patients (t(18)=−0.054, ns) nor for the healthy controls (t(18)=0.000, ns). As can be seen in Fig. 1, no change in subjective well-being from pre- to post-rating was observed in the healthy control group. The rating scores did not change significantly between the two time points of measurement, independent of the allocated condition (sleep condition pre=6.9, post=7.3: t(9)=−0.292, ns, active condition pre=6.9, post=10.7: t(9)=−1.529, ns). Scores of subjective well-being as a function of group (patient, control), time ... Fig. 1. Scores of subjective well-being as a function of group (patient, control), time (pre-rating at 10 a.m., post-rating at 4 p.m.) and condition (daytime sleep, controlled activity). This score reflects the mean calculated from two parallel versions of the questionnaire ((BfS+BfS′)/2). The maximum value is 56 and indicates the complete absence of subjective well-being, whereas a value of 0 reflects a maximum of subjective well-being. The scale was cut at 36. Error bars indicate standard errors of the mean, ⁎⁎p=<0.001. Figure options For the patients with MD different results were found. In the active condition the patients did not show any significant change in their ratings between pre- and post-measurement (pre=26.2, post=21.9: t(9)=1.204, ns). In contrast, a significant improvement in subjective well-being was found by comparing the pre- and post-ratings in the sleep condition (pre=31.7, post=18.0: t(9)=5.117, p=0.001). In addition to the results presented, differences between patients and healthy controls were compared separately for the active resp. sleep condition. These comparisons between the two groups showed that in the sleep-condition significant differences can be found between patients with MD and healthy controls on both points of measurement, with the patient group showing higher scores at both time points (pre-rating: t(18)=−7.306, p<0.001; post-rating: t(18)=−2.297, p=0.034). In the active condition just the pre-ratings for patients and controls were significantly different with higher scores for the patient group (t(18)=−3.905, p<0.001). For the post-rating no significant difference between the two groups was found (t(18)=−1.880, ns). The calculated correlation coefficient revealed a significant correlation between restorative value of sleep the night before study participation and BfS score at the first measurement, r(38)=0.78, p<0.001.