(see also sleep disorders)

Insomnia is a symptom which often accompanies a variety of anxiety disorders. In fact, anxiety itself may often cause what is referred to as ‘paraphysiological insomnia’, where it becomes impossible to fall asleep (even though one is tired and needs to rest) precisely on account of the fact one is over-anxious about having difficulty in sleeping. Anxiety and stress can cause psychophysiological imbalances, which then have an effect on all activities of the mind and body, and sleep is one of these. Cognitive-behavioural psychologists have drawn attention to the finding that anxiety interferes with the length of time that passes before a person can fall asleep, while depression has an effect on the subsequent depth and continuity of sleep. The cognitive-behavioural approach considers disorders and psychological difficulties such as insomnia as deriving from an individual’s incapacity to adapt to environmental stimuli.

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.

There are two main phases of sleep: the REM and NREM phases. During the REM phase, the eyes move with rapid, rhythmic movements. This phase normally occurs 4 or 5 times per night, at intervals of about 90 minutes each. During each REM phase, which will last only for a few minutes, the sleeper will have very intense dreams. REM sleep is also called paradoxical sleep as it is characterised by events that denote a situation that one might consider far from tranquil or ‘relaxing’. During this phase, EEG [electro-encephalogram] readings reveal the appearance of very strong brain waves, which are more ‘agitated’ with respect to those present in a ‘deep sleep’ phase, accompanied by brief apparitions of alpha and beta waves typical of the waking state. In contrast with an increase in the activity of the involuntary muscles (heart and lungs), the voluntary muscles become literally paralyzed.

The NREM phase, which is characterised by deeper sleep, is in turn subdivided into four distinct stages:

  • stage 1: This transitory sleep stage lasts for a few minutes only. Eye movements are circular and very slow;
  • stage 2: Slightly deeper than stage 1. The slow movements of the eyes stop almost entirely;
  • stage 3: Cerebral rhythms become very slow. The very light movements of the eyes cease entirely;
  • stage 4: This is the stage of deep sleep, during which the frequency of brain waves is very low (delta waves).

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.

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