I wrote a lot (1531 words)... thanks, Adderall. Wanted to share my experiences relative to infectedmushroom's post, but it turned into something more like a blog post. Hopefully some of this is of interest, and maybe more can relate and share their own stories.
The short version: I have an actual SPD diagnosis but I don't see much of a point in seeking one out. I have a cushy job where my poor work habits are tolerated, but am scared I won't be able to survive in a less lenient environment and don't know what I'd do if I get to that point. I have few close relationships, and worry about the strain I could put on them since I don't have a big social support network and only have a few people I can rely on. Pharmaceuticals help deal with some negative symptoms, but don't fix the real problems; recreational drugs can but they are ineffective for self-medication and only good for infrequent fun. Depression is the big issue and it's fueled by anhedonia, which can be temporarily overcome with novelty, but a lack of interests makes doing new things hard. I think I would have a much more fulfilling life without this personality type.
Also, saw the edit after I started writing this post - you are probably on to something with sounding self-centered and arrogant. Schizoids can come off as narcissistic. SPD and narcissistic personality disorder are distinct, though, and I think the causes and behaviors are different even though there might be some overlap in how people with either disorder come across to others. IMO the difference is that narcissists are truly self-centered, whereas schizoids are so disinterested in others that the self is all they have.
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There's not much of a purpose in getting a diagnosis for SPD. There aren't any pharmaceutical or therapeutical interventions specifically indicated for it. If you are going for psychotherapy, simply describing your symptoms and asking for help with them is sufficient - the therapist can use whatever diagnosis he/she wishes for billing purposes. It could be useful in some sort of disability claim I suppose. Perhaps it could be useful in getting accommodations so you can avoid situations that are stressful for you. I am considering maybe trying something like that at work so that I get assignments that are more interesting and less stressful. Maybe my therapist can write a letter for me to give to HR, or something, and they can tell my boss to change my workload a bit.
I was diagnosed by a psychiatrist (actually without my knowledge - I saw it in medical records after the fact) and only found out when and how the diagnosis was made months later when I asked my therapist, who had access to the notes. Didn't seem to affect my treatment in any way.
I am able to work effectively in high-stress environments... sometimes. I actually enjoy the stress when working on difficult problems and I'm hypomanic and get way more productive than anyone I work with. It's rare for me to be in that zone... but it's enough to make up for the less productive times. I'm not really good at working a typical work schedule. I was able to do it for a year and a half - worked on time and didn't take days off due to stress/mental health. I wasn't always productive while I was at work, but I got things done on time. I felt miserable all the time, and got burnt out, and quit.
My new job is incredibly flexible and tolerant - awesome because I haven't gotten fired but terrible because it enables all my bad habits. I've probably missed at least fifteen weeks total in the less than two years, between being on actual disability, being actually sick (flu/sinus infection or recovering from surgery), being on actual vacations, or not working due to depression/disinterest/stress. And my work schedule is erratic - we have flexible schedules, and can work from home often, but I take full advantage of that. I spend less time than others in the office when I do go in, and don't always announce that I'm working from home ahead of time (which is expected as a courtesy). I make up for all for all of this by being a very valuable and productive employee when I am actually working. It's the combination of bipolar II and schizoid personality disorder that causes the problem - things go awesome when I'm hypomanic, not too bad when I'm in the middle, and I just fall apart when I'm depressed.
I'm actually really scared to get another job, whether I do it out of necessity or choice (I could get more money elsewhere) - it's unlikely I'd be able to find another one as lenient. It's not exactly something that would be advertised as part of a benefit package or I could ask about during an interview. If I did find an environment where my behavior would be tolerated, I'd probably have to put in a solid six months or so of awesome performance before I could get away with it. It makes me wonder what happens next if I lose my current job - I could probably get another one quickly as long as I am feeling good enough during the interview, but can I actually last through the first month? It probably all depends on whatever state my mood is in at the time.
If the depression and mood swings don't get controlled, and I can't maintain the anti-schizoid mask well enough, I feel that there's a good chance I'll end up unemployable in my current field at some point, and won't be able to maintain my current lifestyle at all. At that point what do I do? Try for disability? Live more cheaply and find an alternative work style, with reduced hours, or occasional projects followed by longer periods of rest/relaxation/recreation? While those are possible, getting that kind of arrangement seems like it would be difficult being schizoid since it's harder for me to build and maintain relationships with people who might be potential clients in a contracting situation.
I have a few close relationships that have lasted for years. I haven't developed any new serious friendships in a long time. Almost all my social interaction is online, on forums, with the few friends I have, or occasionally with people from school or previous jobs that I am still in contact with. I occasionally do things with my friends, but not that often.
Drugs help with some things. Wellbutrin gives me a motivation and wakefulness and interest boost, some of the time, and Vyvanse often gives me focus. Both can make me social but only when it's something I really want to talk about. So it's no good if I want to make casual conversation, and not if I want to meet people, unless it's at a venue full of people with similar interests (like this forum). GHB/analogs as well as serotonin releasers like 6-APB can make me genuinely chatty and able to interact with random people much better, as well as deal with anhedonia and avolition, but they are too intoxicating and dangerous for anything other than recreational use IMO. I'm wondering if the right MAOI could provide the right mix between motivation, mood elevation, and enjoyment, possibly in synergy with other drugs.
Anhedonia is my baseline state when not on drugs - but it can be overcome with novelty. I can get excited for some video games or TV shows, but not many. Something really big can trigger hypomania, like moving to a new place that I'm feeling good about, or going on a vacation to some place and loving it. I don't really have strong enough interests to try many other new things. I could travel to a lot of interesting places I suppose, but there's not that many I'm willing to go to alone, and I don't have anyone to travel with. And when I do travel it's rare that I truly enjoy a place a lot.. partly because I don't have interest in trying cool activities, like scuba diving if I'm in Hawaii. A city like NYC is awesome if there are a lot of interesting events/shows going on at the time. I live around an area that has tons of cool things to do and I don't have the motivation or interest to do much of anything save for the occasional concert. Even buying a faster car (or renting one!) and driving around on scenic highways once a month would probably help.
I don't really like or dislike my personality so much - it's mainly the depression component of bipolar disorder that is the problem, and anhedonia fuels a lot of that. Although I'm not interested in establishing new relationships, I have some concerns about not having effective social support, and depending too much on the few close connections I have if/when I need them. I do see a lot of locked potential in myself, but focusing on how things COULD be is not productive without realistic proposals to actually do better.