This article seems to be mostly speculation and is frankly weird in its assertions.
The very definition of depression is unproductive behaviors, and patterns of thought that go in circles.
There is a productive emotion that causes both reflectiveness and social isolation; it's called "sadness". People often describe a period of mourning as a necessary downtime, a reconfiguration, to get ready for the rest of one's life. I have never heard anyone describe depression as anything other than a waste of time.
Some problems with the speculation, known to anyone who has read about or dealt with depression:
* Difficulty concentrating is one of the symptoms of depression. You can't think.
* Depression typically begins for no apparent reason in the person's life circumstances. It's often seasonal, triggered by things like changes in the length of the day.
* Depression doesn't lift when you've solved a problem. It lifts for no apparent reason, too.
* Depression is often fatal.
A better speculation: depression is a disorder of the circadian rhythms.
Reading over a few of the abstracts, the consensus appears to be that depression can be caused by defects in circadian rhythm, but that the relationship isn't necessary, and may not be sufficient. If I were you, I'd ease off on using "amateurish speculation" as an epithet in this situation.
Difficulty concentrating is a tricky symptom. Depressed people may have difficulty concentrating on what they want to think about, but they may ruminate obsessively on unpleasant topics. That fits nicely with the article's speculation that depression is "nature’s way of telling you that you’ve got complex social problems that the mind is intent on solving."
"There is a productive emotion that causes both reflectiveness and social isolation; it's called "sadness". People often describe a period of mourning as a necessary downtime, a reconfiguration, to get ready for the rest of one's life. I have never heard anyone describe depression as anything other than a waste of time."
What the article is trying to describe is the theory that the neural mechanisms that enable reflectiveness are also responsible for depression; the theory argues that the former trait presents a selective advantage, but that defects in the process result in depression.
Neither the theory nor the article (in my reading) are arguing that depression is a beneficial outcome -- only that depression may be an inevitable, occasional result of having the capacity for reflectivity and sadness. It's a hypothesis for why depression isn't more rare than it is.
Yes, it's amateurish speculation, but it does contain a useful point which you have missed. Perhaps pathological, clinical depression should be seen as the pathological manifestation of a valuable adaptation. Depression might be kind of like the immune system: a valuable mechanism that sometimes goes crazy and causes harm. By defining depression as "unproductive behaviors, and patterns of thought that go in circles," you reserve the term depression for pathological forms of depression, which might not be the best way of looking at it.
"I have never heard anyone describe depression as anything other than a waste of time."
What does that mean exactly? I think the reason why teenagers and young adults are depressed is because they are trying to figure out what the world is and what is their place in it. Sorting out their fundational believes and what not, like what career to choose, or whether it matters if there is a god, or whatever and I wouldn't call that a waste of time.
The page you linked to defines "Major Depressive Episode" and "Major Depressive Disorder." Even mental health professionals use the term more broadly than that.
The very definition of depression is unproductive behaviors, and patterns of thought that go in circles.
There is a productive emotion that causes both reflectiveness and social isolation; it's called "sadness". People often describe a period of mourning as a necessary downtime, a reconfiguration, to get ready for the rest of one's life. I have never heard anyone describe depression as anything other than a waste of time.