To sum up why I feel this specific set of personality traits was from nature rather from nurture in my case:
First, I'm an extremely close match to the ones described in the DSM and ICD, with no factors missing or mismatching in those two. It just seems a lot more likely to me that such a close fit would happen if the cause were physical rather than environmental. The idea being that the environment is more variable, malleable and unlikely to give consistent results.
The fact that this well-delineated grouping of 'symptoms' reoccurs enough for it to become a diagnosis is a strong indication to me that it's something physical. I have some background in biology, and when studying genetic disorders this kind of pattern shows over and over: some single translation protein gets fucked up somewhere, the signal it was supposed to send is lost and it all cascades through the signaling pathway to produce an array of seemingly unrelated symptoms that nonetheless have a single discrete (or close to it) physical cause. My thinking is that it just happens that in this case the symptoms all happen inside the brain and are a little fuzzier and more well-hidden than something like, say, epilepsy.
Second, I was an extremely normal boy in a normal upbringing before the (rather pronounced) onset of it around age 11-13. I had no trauma, I had nothing bad happen to me, no accidents, nothing. It just happened by itself with no apparent prompting. It has also not once wavered and my preferences haven't given any sign of shifting in the near 20 years since.
Again, this is just my perspective and I have no hard evidence. I'm also not denying that in other people's cases the environment may have a greater impact: human beings aren't isolated systems, and it's not predictable how some trauma or how you were raised will interact with a developing physical brain chemistry disorder: things are rarely as clear cut as my case apparently is when it comes to mental development and issues.
Even if I'm right and it is actually a physical 'disorder' in the way I'm thinking, I have to imagine it would also fully possible to arrive at the same or very similar 'symptoms' through a separate path even if you don't have it.
>when you just felt like not socializing anymore and getting depressed
I should address this, because I think it's an important distinction. I didn't become depressed or even sad when I lost the will to socialize. I went on just fine through middle school and high school for a good 6 years, barely participating in school social life, until I went into university. There, the social isolation and lack of drive caused actual practical problems. I was failing my classes, my future looked bleak, and THAT caused depression. If I missed a class (which I often did) I couldn't ask anyone for help, because I didn't know anyone and didn't want to anyway.
Mainly it was the lack of drive. I think most university students, when they see a looming deadline, will get anxious. I just felt nothing, so I did nothing, so I dropped out, so I had no good prospects, so the future was looking worse and worse. It would've been extremely easy to fall into the stereotypical longer term NEET life of relying on your parents but by luck I managed to pull myself out after only about a year.
If I had been born some kind of trust fund baby and knew I would never have to work in my life I would have continued coasting through life just fine and happy, never gotten depressed, and never attempted suicide.>>7546
Well, you're not exactly wrong, but you're missing my point. What I'm saying is that I think there's a specific bodily cause of some sort that generally gives rise to this particular set of personality traits. I could rephrase that into something like 'personality traits X Y and Z that are associated with SPD made my life a lot harder', but you get my meaning.