Hello, I'd like to help you with your question. SAD is different than a Major Depressive episode in several key areas, but especially in the dynamics of how it works in the brain. What you have said about Major Depressive disorder (MDD) is primarily true of the recurrent type. With this type of MDD, the body appears to chemically alter certain pathways in the brain such as you mentioned which encourages future episodes of MDD through chemical changes in the brain rather than damage to brain cells. Over time, according to some research, pathways in the brain begin to deteriorate especially in the pre frontal cortex. In some patients, there is further involvement with the hypothalamus. SAD does not operate in this way. Rather, the circadian rhythm regulation of the brain is altered by a lack of full spectrum light. This does reduce serotonin but it does not appear to cause changes in the brain that are similar to MDD. By following light therapy and by taking anti depressant medication with regularity, these symptoms can typically be controlled. In your case, the brain's response is more related to what appears to be sleep/wake cycles. Unfortunately, in some people, this affects them in ways similar to what you have experienced. However, just as a lack of sleep does not appear to cause brain cell damage except in extreme cases (as in REM deprivation), having SAD does not appear to damage brain cells.
I hope this has helped you,
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