Insomnia linked to increased hyperarousal in the morning

Our recent study published in the Journal of Psychiatric Research demonstrates that people with insomnia suffer from consistently elevated levels of hyperarousal – a state marked by persistent psychological distress. This heightened arousal is particularly pronounced in the morning and tends to intensify overnight following poor sleep quality. Targeting sleep quality could therefore be a key strategy for alleviating daytime hyperarousal in insomnia sufferers. 

As a first step, we sought to clarify the concept of hyperarousal, a condition which has been frequently linked to anxiety, insomnia and stress-related disorders. Despite its recognition as a core feature of insomnia, hyperarousal has been applied, defined and measured in numerous ways, posing challenges for understanding its precise nature.  

We therefore recruited 207 participants (aged 18 to 70, 169 diagnosed with insomnia and 38 good sleepers) from the Dutch Sleep Registry and asked them to wear actigraphs, monitoring physical activity, and fill in sleep diaries over a period of 9 consecutive days. Additionally, eight times a day, participants were invited to fill in a detailed assessment of their mood consisting of 41 separate items on their mobile phones. This ecological momentary assessment method resulted in more than ten thousand data points, allowing the use of exploratory factor analysis to examine whether a hyperarousal factor would crystalize in the data. Indeed, a distinct emotional state encompassing feelings of tension, distress, irritability and rumination was found. Subsequently, we examined how this hyperarousal factor changed across the day and night and whether these hyperarousal dynamics differed between good and bad sleepers.  

The study identified several key findings about hyperarousal. Participants with insomnia consistently exhibited higher hyperarousal levels compared to those without sleep difficulties. Although their hyperarousal was elevated throughout the day, it was especially pronounced in the morning and gradually declined as the day progressed. While all participants experienced a morning peak in hyperarousal, the overnight increase was significantly more pronounced in individuals with insomnia. This suggests that people with insomnia may face difficulties in unwinding during sleep, resulting in heightened distress upon waking. 

Using predictive analyses, the researchers highlighted a strong relationship between perceived sleep quality and heightened hyperarousal the following morning. When participants reported the previous night to be of particularly bad sleep quality, increases in hyperarousal levels were more pronounced in the morning. This effect was stronger than the effect of other objective sleep features, such as sleep efficiency and sleep duration measured by wrist actigraphy, on morning hyperarousal, highlighting the known subjective character of insomnia disorder.  

The study lays the groundwork for developing treatments focused on improving sleep quality as a strategy to alleviate daytime hyperarousal symptoms in individuals with insomnia. Given the strong link between perceived sleep quality and morning hyperarousal, treatments targeting sleep quality directly —whether through behavioral interventions like cognitive behavioral therapy for insomnia (CBT-I), mindfulness-based approaches, or pharmacological treatments—could prove especially beneficial. Future research should also aim to better understand the underlying neurobiological mechanisms of hyperarousal and examine how specific interventions might reduce both sleep disturbances and the emotional distress associated with insomnia.