My word... Could they have phrased that any less clearly?
As I understand it: the more depressive symptoms the subjects showed, the less likely they were to actively avoid bad outcomes (unless there was some other associated reward).
ChatGPT, asked to translate to a high schooler: "Basically, this study found that young people with depression sometimes struggle to break automatic habits, especially when they’re trying to avoid something bad and there isn’t a prize or reward for doing it."
OgsyedIE•1h ago
In a scenario where a disaster has negatively affected the primary productivity of the local food web (e.g. volcano, forest fire, bolide, plague or tsunami), the groups of social species that exist in an environment are likely to engage in internal strife until the food web productivity the group subsists on has returned to normality. Phenotypes which reduce activity across the board without making any changes to their distribution of activities, just hoping for things to get better on their own, are likely the phenotypes that are most successful at surviving to reproduce within conditions of intragroup strife when these infrequent disasters occur.
If this line of reasoning bears out to correctly describe the actual selection pressures that have led to the genes for depression evolving, it follows that what we call major depressive disorder is in fact the genome seeing and carrying out false positives for needing the famine-survival strategy.
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Incidentally, I first came across the theory I'm repeating here on Steven Byrne's neuroscience blog, if you want an avenue for finding sources.
SamoyedFurFluff•1h ago
My understanding is the existence of selection does not necessarily mean every trait that exists right now has an evolutionary benefit. It is more coarse grained that anything that doesn’t prevent you from breeding is acceptable. Depressed people are not made infertile by their depression, so there will be a subset of depressed people (assuming depression even has a hereditary component). This doesn’t mean the trait of depression has an advantage in order to exist, it just isn’t so much of a disadvantage that it doesn’t exist.
andoando•59m ago
Only the system as a whole must carry superior fitness, not each of its individual components. Given a sufficiently complex system, its rather expected that there will be negative, or even outright destructive functions that arise. You can certainly try to find a positive reason for why cancer, disease, death during conception, etc exist, but there is a much simpler explanation.
Depression in this view, isn't something outright that was adaptively constructed, but merely a side effect of how the mind works.
mothballed•55m ago
Note: this is a speculation, not assertions of fact
Filligree•47m ago
Evolution functions not at the level of groups, or even individuals, but genes inside of individuals.
Most of the time thinking of it as group selection at the genetic level (=individuals) does work, fortunately.
mothballed•41m ago
andoando•43m ago
Its entirely normal to be negative, or to ignore stimuli, or decide not to do things. In some situations, say if you were trapped in a cage your whole life, you'd agree it'd be entirely normal to be depressed. It would make no sense to waste energy running around hitting iron bars that won't break.
In this sense, depression is somewhat of a social construct. We determine someone is depressed because we believe their reaction to the environment to not be normal.
OgsyedIE•42m ago
mothballed•35m ago
Imagine for a moment, a version of depression that appears after someone gets their reproductive member cut off (perhaps encounter an angry lion?), but they are still around to compete for food with the extended family's children.
bubblyworld•46m ago
Totally agree with your first sentence though. And even if there is a plausible adaptive function it may have only been adaptive in the past, or might be a side effect of some other adaptive function (see sickle cell anemia), or a host of other possibilities.
Consultant32452•20m ago
thfuran•17m ago
schmidtleonard•58m ago
munificent•40m ago
Patience, "biding our time", "hunkering down", etc. are actual emotional states we can experience and recognize, and depression doesn't feel even remotely like for most people as far as I'm aware.
Also, this explanation would only really work if the entire group entered a dormant depressed state together. Otherwise, the non-depressed ones would capitalize the tribe's resource and everyone would still end up screwed. But depression doesn't seem to have that sort contagious social component. On the contrary, when someone is depressed, the immediate response by people around them is generally try to "cheer them up" or encourage them to exit that depressed state. And while the depressed person is likely conveying a whole lot of negative sentiment, most aren't actively attempting to get the people around them to be depressed too. That's the last thing most depressed people want.