What is SAD

• SAD is a particular type of infradian rhythm called a circa-annual rhythm as it is subject to a yearly cycle.
• However, it could also be classed as a circadian rhythm as the experience of SAD may be due to the disruption of the sleep/wake cycle and this can be attributed to the prolonged periods of daily darkness during winter.
• The hormone melatonin is implicated in the cause of SAD.
• During the night, the pineal gland secretes melatonin until dawn when

  there is an increase in light.
• • This is a depressive disorder (described in DSM-5) with a seasonal pattern.
• As with other forms of depression, the main symptoms of SAD are persistent low mood (affect) alongside a lack of activity and interest in life
• SAD is sometimes called the ‘winter blues’ because sufferers tend to experience depression during the winter months (September to February) when the number of daylight hours becomes shorter
• •During the winter, the lack of light in the morning means this secretion process continues for longer.
• • This is thought to have an effect on the production of serotonin in the brain, which is the neurotransmitter linked to the onset of depressive symptoms.
• Melatonin is a pre-cursor for serotonin, melatonin stops being produced when light is present and this is when serotonin is produced.

  But because it stays dark for longer in the winter, the secretion of serotonin is delayed = depression!