der||1.02||1.24||−1.43 to 3.57||.39|
|Age||0.61||0.43||−2.66 to 1.48||.17|
|Intercept||8.87||13.63||−18.61 to 36.34||.52|
|Time||−2.06||4.58||−11.42 to 7.29||.66|
|Gender||−7.77||15.15||−38.32 to 22.78||.61|
|Age||0.004||1.03||−2.06 to 2.07||>.99|
|Time×gender||−1.82||0.96||−3.79 to 0.16||.07|
|Time×age||0.08||0.34||−0.6 to 0.77||.80|
|Gender×age||0.71||1.13||−1.57 to 2.98||.54|
aISI: Insomnia Severity Index.
bPSQI: Pittsburgh Sleep Quality Index.
This study compared self-reported insomnia symptom severity, sleep quality, sleep characteristics, and CBT-I treatment response between adolescent girls and boys with at least mild symptoms of insomnia. The results supported some of our predictions by showing that girls more often than boys reported sleep characteristics consistent with disturbed sleep, including increased nighttime wakefulness and reduced sleep efficiency. However, contrary to predictions, we found no differences in self-reported sleep quality on the PSQI or in difficulty falling asleep, and gender differences in symptom severity and total sleep duration were accounted for by boys being marginally younger in age. It is not immediately clear why girls reported sleep characteristics consistent with disturbed sleep but not poorer sleep quality on the PSQI or insomnia symptoms on the ISI (when controlling for age) compared to boys. One possible explanation is the nonclinical sample examined in the current study. Individuals with milder symptoms may experience greater symptom fluctuation consistent with individuals in the early stage of disorder development (prodromal phase; eg, ), which may be more effectively captured in state-based measures (eg, daily sleep diary) compared to trait-based measures reliant on self-report (eg, PSQI and ISI measure sleep parameters over the past 4 and 2 weeks, respectively).
Increased wakefulness after sleep onset in girls in the current study is consistent with previous reports showing women and adolescent girls more often report sleep characteristics consistent with increased nighttime wakefulness [, ]. However, unlike these previous studies, we did not specifically find that girls reported more difficulty falling asleep. The previous studies were conducted in adults and in a cohort of adolescents with an average age of 17 years (compared to 14.5 years in the current study), which might account for these differences. Regardless, our results indicate that gender differences in sleep characteristics in older adolescents and adults are at least partially present in younger adolescents (in addition to reduced sleep efficiency in girls). One possible explanation for increased sleep disturbance in girls is the propensity for adolescent and adult females to engage in unhelpful cognitive processes, such as rumination and worry, relative to males [ , ]. Rumination and worry play a central role in sleep disturbance in a range of contexts, including in individuals with sleep disturbances [ ], individuals with other mental disorders [ ], and healthy individuals [ ]. For example, Harvey’s [ ] cognitive model of insomnia postulates that excessive worry about sleep and the consequences of poor-quality sleep triggers autonomic arousal, emotional distress, and excessive monitoring of threats to sleep quality (eg, indicators of insufficient sleep or poor functioning during the day), which ultimately results in real deficits in sleep. Thus, established gender differences in worry make these factors that are critical to the development and maintenance of sleep disturbance good candidates to explain gender differences shown in this study. Future studies could employ measures of rumination and worry alongside sleep measures to determine the extent to which they moderate gender differences in symptoms.
Adolescence has been identified as a period of substantial change in terms of biopsychosocial development, which has been attributed to changing sleep patterns in both genders in this age group . However, pubertal maturation seems to be particularly significant for girls in regard to sleep. Several studie