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The role of stressors in the genesis of chronic insomnia has been documented in a number of studies. In a retrospective assessment of good vs poor sleepers, those with insomnia reported significantly more negative life events, such as losses and illnesses, during the year prior to the onset of insomnia, and many specifically attributed their insomnia to a major life event.[1] In a prospective study of young adults assessed over a 7-year period, those who experienced more frequent negative life events and interpersonal conflicts were more likely to have occasional insomnia or repeated bouts of brief insomnia.[2] In addition, a Finnish study found that psychosocial stressors were more likely to be associated with insomnia than were health problems,[3] indicating the strong link between stressors and sleep problems.
Although major stressful events can trigger insomnia, chronic exposure to minor stress may also contribute to an increased risk for insomnia and may be particularly important in the genesis of chronic sleep disturbance. In a population-based study in Japan, insomnia was significantly correlated with daily stress levels, whereas regular exercise was negatively correlated with sleep problems.[4] A recent study of over 3400 male civil servants in Japan assessed the relationships of a variety of stressors on 3 aspects of insomnia: difficulty initiating sleep, difficulty maintaining sleep, and poor-quality sleep.[5] Higher perceived stress, the consideration of life as not meaningful/worth living, and a variety of job-related stressors showed the strongest independent associations with all 3 types of insomnia complaints.
Recent work has begun to look more closely at the effects of specific stressors on insomnia. Some of these studies have demonstrated relationships between family conflict and insomnia in children, adolescents, and young adults, consistent with the idea that early and chronic stress may contribute to lifelong sleep problems. In a study of French adolescents, those who had insomnia symptoms came from families with higher divorce rates, had poorer relationships with their families, and reported higher rates of medical and psychological illness or death in parents.[6] A prospective study of undergraduate college students assessed the impact of family, academic, and social events on insomnia; controlling for depression, negative family events, but not academic or social stressors, showed modest but significant predictive value for insomnia.[7] Furthermore, there appeared to be an interaction between family and academic stress, in that individuals who reported high stress levels in both of these areas had the highest insomnia scores. It is also likely that sleep problems in children may lead to increased family stress, as treatment of children's sleep problems has been shown to improve family satisfaction.[8]
Other studies have focused on the role of work-related stress in the development of insomnia. Individuals with insomnia frequently attribute their sleep problems to work-related stress or job dissatisfaction.[9,10] Job factors, such as shift work and frequent travel, particularly across multiple time zones, are also known to contribute to circadian rhythm sleep disorders and resulting insomnia. In turn, insomnia is significantly associated with decreased productivity and increased absenteeism.[11,12] A Swedish study found that a poor psychosocial work environment led to a more than 2-fold increased risk for the development of a new episode of insomnia.[13] Several studies have suggested that increased workload pressure is a risk factor for sleep problems.[14,15] A prospective, 1-year study examining the effects of specific work stressors found that work demands, leader support, and influence over decisions were significantly related to the development and maintenance of insomnia.[16] A cross-sectional study performed in Japan also found that increased job stress, as indicated by an effort-reward imbalance and overcommitment, was associated with insomnia.[17] Furthermore, another Japanese study reported that high job stress was not only associated with a higher risk for insomnia, but also for short sleep (less than 6 hours per night), suggesting that work-related stress may contribute to a combination of both insomnia and sleep deprivation.[18]