Seasonal Affective Disorder bis

Date: 28/01/2011


Petrolo Alessia


Seasonal depression or SAD (Seasonal Affective Disorder), belongs to the group of weather-diseases. It is a type of depression characterized by mood deflection caused by seasonal climate changes and the decreasing hours of sunlight. The onset of symptoms usually occurs in autumn and regress at spring.
To diagnose SAD is necessary that the symptoms appear without a clear psycho-social cause, such as the absence of stress. In addition to a poorly modulated and deflected mood, people who suffers from SAD have a lack of energy, tendency to avoid social life, inability to concentrate and low attention, a low sexual desire, sleepiness and increased appetite (especially for carbohydrates and sweets).

All living beings perceive changes in the intensity of light during the day; in the course of evolution they developed cellular mechanisms in order to regulate their biological rhythms according to light and to adjust their daily activities into a 24 hours cycle.
Circadian rhythms in human beings, are modulated by a biological clock, located in the hypothalamus, represented by the suprachiasmatic nucleus (SCN), sensitive to many factors, such as exercise, food availability, temperature, employment, and especially light stimulus.
The light stimulus modulates neuronal activity of SCN. directly through the hypothalamic-retina via and indirectly through the lateral geniculate complex. From SNC the major output reach the paraventricular nucleus of the hypothalamus (PVN), site of activity of the autonomic nervous system, and the pineal gland where there is the synthesis of melatonin. SCN activity is also modulated in an inhibitory way by the serotonin system coming from the raphe nucleus.

Human body receives the full range of light waves through eyes and skin. The radiation which passes through the eyes are transformed into electrical impulses and transmitted via the optic nerve to the brain: the impulses reach the hypothalamus where there is an increase of serotonin and the epiphysis, where they inhibit the production of melatonin( a hormone-sensitive to light-dark cycles).
Some studies suggest that neither the rods nor cones, the retinal photoreceptors involved in the transmission of visual information to the SCN, are necessary intermediaries of the effects of light; there is in fact a system of retinal sensitivity formed by ganglion cells specialized, located at the origin of hypothalamic -retina tract , suited to the integration of spatial light stimulus. These cells use a pigment called melanopsin, which has the highest sensitivity in the blue part of the visible spectrum, near 480 nm; studies have established that exposure to intense blue monochromatic light (460 nm) affects more the circadian rhythm than the green ones (555 nm, peak sensitivity of the cones). Therefore the physiological effects, such as increased body temperature and heart rate, are strongly dependent by the wavelength and they are bigger with an exposure to a monochromatic light of 460 nm (blue), than the one of 550 nm (green).

Depression is usually treated in clinical with antidepressant drugs and / or psychotherapy. In cases of SAD, the classic tricyclic antidepressants are avoided because they exacerbate the sleepiness and lethargy, and SSRIs are preferred.
Since the early Nineties the seasonal mood disorder, in its depressed phase,is threated with light therapy or phototherapy.
The basic mechanism of this therapy is simple: the light passes in the optic nerve, stimulates neurons and modifies the production of the” hormones of well-being“, specially serotonin and melatonin, which are able to interact with mood but also with metabolism, appetite, sleep-wake cycle, the sense of fatigue or vitality.
Generally, the light therapy sessions are carried out in autumn or winter when less sunlight makes appear first symptoms of seasonal depression.
During these sessions patients keep eyes open, about 60-70cm from the light source, a sophisticated lighting system made by special fluorescent tubes with advanced technology which diffuse, through a inclined broad,a large spectrum light, similar to the solar one.
Recent studies have shown that different wavelengths correspond to different effects on the body: for example wavelengths corresponding to red (red light terapy )are used to solve skin problems, on the other side wavelength due to the color blue are most commonly used in the treatment of depression.
First hours of the day are the more appropriate for exposure; the exposure time ranges from 40 minutes to 3 hours a day with a lighting system that makes 10000 lux, equivalent to a light intensity 20 times than a typical interior one.
The first signs of improvement in depressive symptoms are already observed in 4 or 5 days , however the treatment is usually maintained from 7 to 14 days.
There are no significant side effects assessment; however they can be reduced during therapy sessions acting on light intensity and distance from the light source.
Since the therapeutic action of light place through the eyes , light terapy is contraindicated in patients with diabetes and suffering from specific diseases of eyes or retina.

There are also natural remedies that may be helpful in the treatment of seasonal depression:
- Magnesium, which is used in states of anxiety, premenstrual syndrome. You can find it in the form of powder or tablets to be taken several times a day but there are also foods which contain large quantities like chocolate and nuts
- Rhodiola rosea, a plant that acts as an adaptogen, it helps our body to counter the negative effects of stress and to better adapt against our disturbs
- Ginseng, a plant with toning and stimulating effects, that can contrast the state of apathy, torpor and low sexual desire
- Chocolate increases the levels of endorphins, substances with a euphoric effect
- Red wine ,that is rich in melatonin

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