Around 90% of prisoners have some sort of mental disorder including personality and substance misuse disorders [22]. The high prevalence of mental disorder, physical health problems, substance misuse issues and prescription medications within prison settings may also compound premorbid sleep disturbances, given the recognised relationship between sleep and health [3], [4], ∗[23] and [24]. Due to the nature of the prison regime normal sleep-wake patterning may be affected through interruption of usual daily routines [25]; forced contact with others [26]; fear of violence [27]; and lack of autonomy [28]. Features of the physical environment are also likely to confer further disturbance to sleep-wake regulation including exposure to extreme hot or cold temperatures [29]; experiencing too much or too little light [30]; excessive noise [30] and [31] (e.g., cell doors slamming, prisoners shouting, keys jangling etc.); and inadequate bedroom setup (e.g., poor mattress quality) [32]. It is not known what non-pharmacological interventions for insomnia are offered across the prison estate internationally, however some general interventions have been recommended in the United Kingdom (UK) policy literature, including psychological therapies, lavender, milky drinks and sleep hygiene advice as preferable to prescribing medication [28].
There has been only one other review conducted in this area to date. In a scoping review published in 2007, Elger [33] asked three research questions: 1) are sleep complaints in prisoners caused by substance misuse, post traumatic stress disorder and mental disorder including insomnia; 2) is insomnia situational; and; 3) what is the importance of reactive anxiety and depression due to being imprisoned compared to prison environmental factors (e.g., light, noise etc.). The review included nine research studies in its analysis, however inclusion and exclusion criteria were not identified and there was no objective evaluation of study quality. Thus there remains the need for an up-to-date rigorous review, which examines these factors. Therefore, in this integrative review we collate, describe and discuss the available insomnia-prison literature, identifying key themes for research and practice. The paper will critically reflect on the method and quality of conducted studies, and outline a thorough research agenda, delineating a series of studies required to further elucidate the prevalence and management of insomnia in prison settings.