By Emma Baker, PhD Candidate
(Supervisor: Associate Professor Amanda Richdale)
There is an abundance of literature that shows children on the autism spectrum experience a significantly high rate of sleep problems, primarily insomnia symptoms, in comparison to children generally and children with other developmental disorders. However, there is much less research that has assessed sleep problems in adults on the spectrum. Our knowledge of the causes of sleep problems in ASD is also very limited. Therefore, my PhD research aimed to explore the types of sleep problems experienced by adults with autism as well as exploring their potential causes. Thirty-six adults with a diagnosis of ASD and no intellectual impairment (21-44 years) and a comparison group of 54 neurotypical (NT) adults (22 to 43 years) took part in my study. While no-one in the comparison group had a diagnosed mental health problem 15 adults on the spectrum were medicated for a comorbid diagnosis of anxiety/depression. Participants completed various sleep questionnaires, a 14-day sleep-wake diary, 14-day actigraphy assessment (objectively measures sleep) and provided seven saliva samples.
Study One assessed various sleep difficulties and disorders in adults with ASD and the comparison group. The results showed that adults with autism took a significantly longer time to fall asleep, had more brief arousals from sleep, and had poorer sleep quality compared to NT adults. Supporting these findings, a significantly higher proportion of adults on the spectrum met criteria for insomnia in comparison to NT adults. These findings are consistent with the findings that are observed in children with autism. Interestingly, nearly half of the adults on the spectrum had atypical timing of sleep and this was more common than for NT adults. Some adults with autism had very delayed bedtimes (later than 1:00am) while others had very early (advanced) bedtimes (earlier than 9:00pm). Such difficulties can have a negative impact on the ability to obtain and maintain employment.
Study Two assessed evening salivary melatonin levels in a sub-sample of ASD and NT participants and investigated the relationship between melatonin and sleep difficulties. Melatonin is a hormone that is secreted during the night and has been closely linked with sleep. My findings showed that adults with autism medicated for a comorbid diagnosis of anxiety and/or depression had lower melatonin levels in the evening before sleep compared to both NT adults and adults on the spectrum and no comorbid diagnoses of anxiety or depression. Those adults on the spectrum with no comorbid diagnosis of anxiety and depression had similar evening melatonin levels to NT adults. We also found that lower melatonin levels were associated with poorer sleep quality in some adults with ASD.
Study Three examined evening cortisol levels, self-reported measures of arousal and sleep difficulties and the relationships between these variables. Cortisol is a hormone that is released in response to stress and has been closely linked with both anxiety and sleep. The findings of this study showed that higher cortisol levels and reported somatic arousal symptoms (e.g., heart racing) before sleep were associated with longer night-time waking episodes and reduced sleep quality in adults on the autism spectrum.
Overall my research showed that poor sleep quality and insomnia continue to be common in adults with autism, however problems associated with irregular sleep timing are more common that has been reported in children. The ability to self-select bedtimes, the presence of anxiety and depression, and unemployment may contribute towards these sleep problems. Low melatonin levels or irregular timing of the night-time melatonin rise time may also contribute to difficulties associated with sleep in some adults with ASD. Lastly, increased arousal symptoms contribute to poor sleep in adults on the autism spectrum. Treatments aimed at reducing arousal prior to sleep may be beneficial; however research is needed in this area.
Based on these findings it is recommended that if you are concerned about your sleep or your child’s sleep, you should get a sleep assessment so that any treatment can be appropriately tailored to your specific difficulties. General information about a range of sleep problems can be found on the Sleep Health Foundation website.