There's new evidence that depression is not just a disorder of the mind.
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I understand your bias towards addition study and repeated behaviors effecting the limbic system, but there are sociological perspectives not being addressed.
You state that,
"...repeatedly, studies are finding a strong correlation between depression and the amount of time spent online."
"Dr. Carnes when describing sex addiction....
....I am finding that the lack of skills for achieving emotional intimacy leads to social anxiety and avoidance."
This leads me to wonder if the Depressed find the internet rather than the internet depressing them.
How can parents "unplug" their holiday gift list?
Behaviors can be just as addictive as ingested drugs.
Tiger Moms and digital media: Parenting in the Digital Age
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