The exact cause of SAD is unknown. However, current opinion suggests that there is a strong link to biochemical imbalances in the brain, caused by lack of bright daylight during winter months.
Symptoms
The SAD Association lists the following symptoms of which some or all can be related to Seasonal Affective Disorder:
- Sleep problems oversleeping, not feeling refreshed upon waking, needing to sleep during the day, inability to get up in the morning
- Lethargy fatigue throughout the day and inability to carry out normal routines due to tiredness
- Overeating craving for carbohydrates and sweet foods (resulting in weight gain)
- Depression loss of self-esteem, feelings of guilt and misery, loss of feelings, apathy, and sometimes despair
- Loss of libido decreased interest in sex and physical contact
- Social problems Irritability and desire to avoid social contact
- Anxiety Tension and inability to tolerate stress
- Mood changes extremes of mood, and in some cases, periods of hypomania (over-activity) in spring and autumn.
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Most sufferers also show signs of a weakened immune system, and become susceptible to more infections and illness than normal.
In its most prominent form, SAD is a serious depressive illness that disables the sufferer and causes severe problems in functioning at work and in the home.
Sub-syndromal SAD, or winter blues, does not normally require medical help, but still has a noticeable impact on mood and productivity.
History of SAD
SAD was first recognised over 20 years ago by Dr. Norman Rosenthal, an American psychiatrist. He states that the medical profession now accepts the importance of the seasons in relation to general health and brain chemistry, which has led to SAD being acknowledged as a genuine medical condition.
This acceptance has prompted a great deal of research into the causes of SAD and possible treatments.
Current thinking
The main consensus is that biochemicals and hormones produced within the body play a huge role in the condition, some of which are explained below.
Melatonin is a hormone secreted by the pineal gland in the brain. It is mainly produced at night during sleep, when the person is not exposed to light. It has a strong effect on the bodys circadian rhythm one of the internal body clocks.
The production of melatonin is suppressed by bright light typically when we wake up in the morning and are exposed to sunlight.
It is possible that this cycle is disrupted during winter months, causing imbalances in the circadian rhythm, and symptoms such as lethargy and over-sleeping.
Serotonin, or 5HT, is known to affect mood. Many treatments for depression already focus on the way that the brain utilises this vital neurotransmitter. To read more about this, click here.
Recent evidence shows that exposure to bright light is linked to an increased production of serotonin. The pineal gland relies on serotonin to create melatonin which provides an interesting link for researchers to follow in the future.
The hypothalamus can be described as one of the brains central control centres. It has nerve connections to most other regions of the nervous system, and affects automatic responses such as the release of adrenaline during times of danger, body temperature, and levels of glucose in the blood.
It is also involved in regulating sleep, motivating sexual behaviour, and determining mood and emotions.
Due to its connections to other parts of the brain, and the fact that it secretes hormones, the hypothalamus has a direct impact on the function of other control centres such as the pituitary and pineal glands.
Light stimulates the hypothalamus through a chain reaction of electrochemical signals. If there is not enough light to start this process properly, biochemical imbalances may occur, increasing the likelihood of SAD.
02/06/2009