Causes of seasonal affective disorder - SAD - winter depression

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The causes of SAD are not fully understood but factors like living in higher latitudes, reduced daylight, low temperatures, hormone regulation and short days seem to be causes the disorder.
Bright light induces certain chemical changes in brain and stimulates hypothalamus, a part of the brain responsible for controlling sleep, appetite and mood.
Lack of sufficient light reverses the chemical process in the brain affecting our mood, sleep and activeness. These changes lead to SAD depression.

Disturbed circadian rhythm and SAD disorder

Circadian rhythm or our biological clock regulates our sleep and wakefulness.
The reduction of daylight in fall and winter disrupts the sleep pattern causing depression.

Reduction in the levels of serotonin and SAD depression

Serotonin is a natural chemical found in the brain which being a neurotransmitter has the ability to affect our sleep, appetite and mood.
The levels of serotonin are affected by sunlight and reduced daylight means reduced production of serotonin.
This results in the ineffective transmission of signals from the nerves to brain and causes the disorder.
Affected persons produce less serotonin in fall and winter.

Increase in the secretion of melatonin

Melatonin, a hormone produced by the pineal gland in the brain controls our sleep pattern.
In darkness the gland produces melatonin, helping us to sleep.
In the daylight the production of the hormone is reduced and we wake up. Persons affected by winter blues have been found to produce more melatonin in the reduced sunlight period.

Genetic causes of SAD

Possibility of genetic transmission is suggested in the results of research work on this disorder.
Close relatives and siblings of the SAD patients have been found to develop this depression.
Current topic:
Causes of SAD disorder and depression.

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