Stress and sleep
Experimental studies that manipulate or induce stress in humans, using both physical and psychological stimuli, have shown that stress negatively interferes with the ability to initiate and maintain sleep. It also affects the composition of sleep stages, reducing deep sleep, leaving us in lighter phases of sleep and more vulnerable to environmental disruption, such as light and noise.
Traumatic life events may also impact the content of our dreams, leading to chronic, sometimes nightly nightmares, where the event is replayed over and over again – this can be very common in those diagnosed with post-traumatic stress disorder (PTSD).
It is also often the case that those with chronic sleep disturbance (insomnia) tend to anchor the onset of their sleep problem to a negative stressful life event, typically around family, health or the work-place. Individuals respond to stress in different ways, and this is likely to have a genetic contribution. For those with a vulnerability to stress-related sleep disturbance, it is likely that a stressful event results in excessive physiological arousal (e.g. increased heart rate, stress hormones) and/or psychological arousal (e.g. anxiety), which will directly impact regions of the brain responsible for initiating sleep and inhibiting wakefulness.
While the majority of us will experience a poor night of sleep from time-to-time, as consequence of daily stressors, a smaller proportion will subsequently develop chronic sleep problems. The reasons for the transition from acute to chronic sleep disturbance is a matter of intense research, but both psychological and physiological factors (and their interaction) are likely to be involved. We know, for example, that cognitive behavioral techniques, addressing sleep-related thoughts and behaviors, can be very effective in improving sleep in those with poor sleep. Similarly, sleeping pills which affect neurochemicals involved in the regulation of sleep, are also effective in the short-term improvement of broken sleep.