Summary of Seasonal affective disorder
Transcript for Seasonal affective disorder
Seasonal affective disorder
Recently, the DSM-5 changed the name of “seasonal affective disorder,” or SAD, to “depressive disorder with seasonal pattern.”
The new name isn’t quite as catchy as “SAD,” but it does describe the condition more precisely.
That’s because depressive disorder with seasonal pattern is not really a distinct disease, but rather depression that worsens at the same time each year, usually in the late fall and winter.
So let’s first review depression. Depression, or major depression, is a serious condition where someone loses their sense of life being enjoyable; this feeling of malaise affects every aspect of their day-to-day life, whether they’re working, studying, eating, or sleeping.
The causes of depression aren’t fully known, but it’s thought to involve a deficiency of monoamine neurotransmitters in the brain, like dopamine, norepinephrine, and especially serotonin.
In depressive disorder with seasonal pattern, there’s a strong relationship with the circadian rhythm, the internal clock that keeps your body in tune with the rising and setting of the sun.
At the base of the brain there’s a region called the hypothalamus, and within it are a group of neurons located in a specific spot called the suprachiasmatic nucleus or SCN.
The neurons in the SCN get information about light from optic nerves, and use that information to run the circadian rhythm.
The SCN relays that information to the pineal gland, a tiny, cone-shaped structure near the hypothalamus.
And when it’s dark out, the pineal gland releases the hormone melatonin, which is chemically related to serotonin.
Melatonin lowers your heart rate and body temperature, helping you go to sleep.
When it’s light outside, the pineal gland stops releasing melatonin, and that has the opposite effect by raising your heart rate and body temperature, keeping you awake.
A risk factor for developing depressive disorder with seasonal pattern is having a sleep phase delay, which is when a person’s body produces too little melatonin at night.
This can be due to things like decreased sensitivity to changes in light, problems with the communication between the retina and the hypothalamus, and even exposure to external sources of light, like you might experience with late-night computer use.
A sleep phase delay can result in a person’s internal clock having more than the standard 24 to 25 hours in a day, which means they may not be able to sleep until at least eighteen hours after they woke up that day.
Long day after long day, this pattern quickly becomes exhausting.
It can be hard for anyone to adjust to the late sunrises and early sunsets of winter, especially those who live in higher latitudes.