ANXIETY AND SLEEP
(see also sleep disorders)
In the vision of classical Freudian theory, insomnia can be related to fears a subject may have regarding thoughts, fantasies or frightening dreams that may occur during sleep. Moreover, during sleep, the rational mind cannot effectively control the instinctive, irrational regions of the psyche and insomnia reflects an attempt to perpetuate such control. Above and beyond the possible psychological explanations for insomnia, it has been demonstrated that certain factors may persistently affect the quality of sleep. In particular, studies carried out by psychophysiologists have ascertained that prolonged stress and anxiety activate a series of cerebral/endocrine structures (the hypothalamus-hypophysis-suprarenal axis), which implies an increase in the secretion of cortisol. When present within the organism at levels higher than normal, this substance, also known as the ‘stress hormone’, causes various problems including insomnia and other sleep disorders, depression and a variety of physical symptoms.
What are the functions of sleep?
At any given moment in our lives, we are always in one of the two possible alternating states of vigilance (waking and sleeping), which follow the rules of our internal biological equilibrium. It would appear that certain basic functions for the nervous system and the organism in general are performed and are possible during sleep. If it were not so, it would not be possible to explain the fact that this ‘behaviour’ has survived from the evolutionary point of view. While it is a period during which the organism becomes profoundly isolated from the external environment in terms of sensory-motor activity, sleep is in fact characterised by constant cerebral activity.
Moreover, the cerebral metabolism is only slightly reduced during NREM [non-rapid eye-movement] sleep and in fact returns to the levels typical of the waking state during the nightly REM [rapid eye-movement] sleep phase. Thus, the brain is not inactive during sleep. It elaborates stimuli received during the daytime and triggers ‘data-archiving’ processes, associating stimuli and data, eliminating those which it believes are superfluous, and preparing itself for the next waking-state phase, during which it can use all of the information and notions it has gathered in order to contend with waking reality. During sleep, the brain does not stop functioning but simply becomes temporarily ‘isolated’. In this state it can elaborate external stimuli in a very elementary manner and retains the capacity to react to sensorial stimuli which might warn the organism of the presence of danger, continuing to be ‘vigilant’ with respect to the surrounding environment.
How does sleep occur?
Sleep is thus a process which has the very important and useful biological function of allowing the organism to adapt appropriately to the surrounding environment. Anything that alters this basic sleep-waking equilibrium will become a source of distress. Insomnia, anxiety and depression are undoubtedly reflections of a maladaptive response to life stress. Inversely, an appropriate sleep-waking rhythm, procuring pleasure and satisfaction and in tune with an individual’s lifestyle, reflects the presence of adequate adaptation.
The NREM phase, which is characterised by deeper sleep, is in turn subdivided into four distinct stages:
Sleep cycles: sleep begins in stage 1 and continues through to stage 4 of the non-REM phase, where an individual will remain for 20-40 minutes. Following this point, sleep becomes lighter and the individual will again enter stage 2 of non-REM sleep for 5-10 minutes and then, suddenly, the REM phase. At the end of this phase, the cycle starts all over again. During the course of the night, there is a partial decrease of non-REM sleep (especially of stages 2 and 4) and an extension of the REM phases, reaching a point where the sleeper remains in this phase for 30-50 minutes. There would also appear to be a ‘refractory’ period between each consecutive REM phase, i.e., at least thirty minutes approximately must pass between two periods of REM sleep.