I have ADHD too. And I find super hard to play as a player: it's a cognitive disability like many others. So I GM, because it keeps me engaged and busy.

I recommend making the game more engaging for yourself. Draw the map. Keep notes. Keep the diary. Keep the party shared kit, herd the mules, play a more complicated character.

Otherwise, I just recommend to be more deliberately mindful. Mindfulness helped me a lot with my ADHD, both for daily activities and emotional stability. Try picking up meditation, or going to a mindfulness-orientated buddhist temple near you.

DM and player with ADHD, here.

I agree with Tsojcanth; DMing can often be easier, because I'm forced to stay focused and engaged as I try to stay one step ahead of the party. However, prepping to DM can be miserable, especially when I'm not on my medication.

Here's my recommendations, based on my experience in both roles:

DO:

• Draw! Draw your character, draw what's happening, draw a map, draw rude pictures. Even for neurotypical folks, this can actually improve focus. (Plus, if you aren't already an artist, you'll learn a new skill!)




• Take notes. I'm horrible at remembering to do this one as a player, but I'm good at it as a DM. Your mileage may vary. I just hate taking notes.




• Fidget...carefully. A fidget cube is small and inexpensive, and if held under the table, it can be very subtle.




• Apologize if you slip up. This also depends on your group, of course, but I've been open with my friends about my ADHD; if I zone out and realize I need information, I always start with "Sorry, I zoned out, what was that?". If I get overexcited and interrupt, I apologize and let the other person finish. Saying sorry goes a long way!




• Volunteer to be useful. This can be anything from figuring out initiative order for all the players and keeping track of it (which has the bonus of being useful if your DM is also scatterbrained-- I can't tell you how many times I've almost missed someone because I spaced out!), to physically getting up and helping to tidy up the pizza boxes. Tell the DM what you're doing and why, just stay in the room.




• Do something else. This really only applies to online games, but I will often find a different task entirely to occupy me while other players are doing things that aren't relevant to me. I'll often crack open The Sims and work on building a house, or some other thing I can easily alt-tab away from. I wouldn't do anything like this locally, because it's incredibly demoralizing as a DM.




• Plan ahead! When it's not your turn in combat, an easy way to keep things moving quickly is to have an idea of what you're going to do before the DM calls on you. Circumstances can change suddenly and disrupt the plan, but it's always useful to have a plan.

DON'T:

• Check your phone. This falls under the "demoralizing to your DM" category. It's not fun to look up mid-narration and realize nobody is listening to you.




• Get up and wander off without warning. You don't have to break the flow every time; you could certainly tell your DM outside of the game "Hey, if I'm not doing anything, I might get up and walk a lap around the house/run up and down the stairs/something so I don't get disruptive," which I would personally be fine with.




• Pull attention to your character when they don't deserve or need it. I would rather have a distracted player than a spotlight hog. The spotlight hog hurts the other players; the visibly distracted player just annoys me.




• Fidget in ways that might distract others. This includes stacking dice, rolling dice, or basically doing anything with dice, especially if you don't have a tray, giving them a chance of falling on the floor. This also includes big movements, bouncing your leg in such a way that you move the table, or anything else disruptive. As I mentioned in a comment on another answer, you may not be the only person at the table with ADHD, and you don't want to make their lives more difficult.

Final thoughts: I'm a big proponent of medication, which has helped me immensely, but I recognize it isn't for everyone, and, quite frankly, that's not what you asked. Even when medicated, I still have ADHD, and I will always have it. If you harness it, it can be a wonderful boon to your playing and improv skills; the innate randomness and scatteredness of an ADHD brain can be very useful for coming up with unique and interesting plans and ideas.

Everyone deals with their ADHD differently. The advice I've given here is specifically what I've done, myself, but figure out what works for you. The one thing that has never, ever worked for me is just trying harder to do things like a neurotypical would.

Be like Bear Grylls. Improvise. Adapt. Overcome.

This is not an answer that addresses any game, or game mechanic, because I don't think that is very relevant in this situation. The scope of this question goes far beyond being a problem GM or player, for that matter.

Seek professional help

As someone with a real life degree in Clinical Psychology (2013, BSc), being a part-time teacher that frequently deals with students having ADD and ADHD, and a boyfriend of someone with ADD, I'm not sure if this platform is the right place to find the most comprehensive, or more importantly: the most effective, treatment. If you are serious about taking "ownership of your condition", which is truly great and admirable, I can recommend to seek professional guidance. Talk to your general practitioner, and ask if you can see a therapist that specialises in your condition. I suggest this, because in general people seem to underestimate the difficulties of conditions like ADHD.

There's various ways of dealing with an attention deficit. A qualified therapist is trained to offer (custom) advice and/or guide you in finding your own ways of dealing with your attention span. This way you can find "tricks" that can help you at the table as well. Of course, the actual quality and accessibility of mental health care varies wildly per country. So if that doesn't work out, or doesn't fit your personal needs: some of my close friends have to deal with ADD everyday (similar condition but without the hyperactive tendencies). They found that "alternative" treatments can work really well for maintaining a better concentration, such as mindfulness, meditation and/or yoga.

• 
  Note 1, on first-/second-hand experience: Keep in mind that meditation in itself is mostly just an exercise in observing, while postponing/removing reactions – both emotional and physical. It can, however, have religious intentions or connotations too. If you don't want that, I can recommend Vipassana meditation, or other forms of non-religious meditation. Having read the book by S.N. Goenka on Vipassana meditation myself, doing the occasional meditation, and having a girlfriend with ADD that did the course multiple times (she doesn't take pills), I can say this type of meditation welcomes all nationalities and religions, and more importantly: it enhances concentration (among other things).


• 
  Note 2, on second-hand experience:
  Both my brother and a friend – both coincidentally play in a D&D 5e game that I GM – used to have more issues with their attention span as well. After seeing their general practitioner for a while, and some testing, they discovered they have a form of Sleep Apnea. After this diagnosis they took necessary steps to deal with this sleeping disorder, and ever since their attention is much better! This emphasises my point regarding seeking out professional help.

Personal advice regarding the game

In any case, talk to your friends at the table. Explain to them that "simply paying better attention" doesn't work for you, and that you're taking steps to make it work. From a personal standpoint, I would like to finish with: you taking "ownership" requires time and effort. Having a table that understands that, helps a lot. If their attitude is: fix this now or leave, I would conclude these are no friends at all and you find a game with more caring people. Good luck!

ADHD manifests in different ways for different people, and mitigations that work for one person may not work for another. So ultimately, it is up to you to decide what works.

As a teacher, I have spent many years helping students stay on task and complete assignments. Although, the answers given to the question you linked addresses the GM, there are many suggestions that apply to what you can do also. Based on my experience, I recomend the following as a starting point for dealing with gaming sessions.

1. Find things that redirect you attention back to the game. Pick up a cheap composition journal, and write down descriptions, sketch encounters, draw maps, track combat, etc. This will give you many short term tasks to shift attention between but keep focus on the game.




2. The talking stick. Get some object to be held by the player whose turn it is, and come up with a non-verbal signal to request the stick. You can not speak unless you are holding the stick. This takes practice and has varied results with controlling impulsive out bursts. If this truly, does not help see point 7.




3. Game Breaks. Talk with your GM to arrange preset game breaks, or a signal that you need a game break, but don't abuse it. Taking breaks reduces nervousness/restlessness that may intensify other symptoms. Typical encounters take 45-60 minutes to resolve. If you need breaks more frequently than this, you might consider playing a difference game.




4. Set up a signal with the GM so he can prompt you to refocus without interrupting play. This will also take practice, but if effective the GM or another player can snape your attention back from distractions.




5. Long discussions about rules removes the fun for everyone. If you think the GM made a mistake, mention it then accept his decision. If you still think he is wrong, save the discussion for a game break or after the session. The GM has the power to correct an erroneous decision after the fact; there is no reason to press a matter during the session. Yes, I know patience is difficult.




6. Fidgeting. If it doesn't distract other players, get some dice to roll when ever you think a roll is good. Note: your rolls are simply to occupy your hands and have no impact unless the GM asked for the roll. A fidget . stress ball or something else that can occupy your hand may with restlessness .




7. Make a list of common activities that may be presented to the group such as Haggling with a merchant, disabling traps, etc. Then, sit with the group to decide which character is best at each task. Now, instead of jumping to "I do ...", you can suggest a character do it. This will make impulse comments more constructive to game play.

If something doesn't work, then you need to objectively answer the following questions:

• why doesn't it work?


• can it be modified to be more effective?


• would something else work better?

I have inattentive type ADHD and have player and GM experience with my own brain (obviously :D) and other players with assorted types of ADHD.

Here're some things that have worked for me as an inattentive player:

• 
  Keeping notes about what each character is doing, especially if this is a formal obligation that I've signed up to do to help remember quotes or to help the GM prep the next session. I like being helpful, and feeling like I might let someone else down is a great motivator for me. The process of note taking gives my hands and brain something to do while keeping me focused on the game.


• 
  Knitting, needlepoint, or spinning yarn, especially if the pattern is fairly easy. I always check with a GM before bringing my knitting to a session, but I've found it's a quiet, not very distracting way to stim. I made it through college largely by being allowed to knit in class.


• 
  Volunteering to physically stand and manage the group's map or initiative. Most of my early experience happened in person in assorted classrooms where GMs typically used the available whiteboard/chalkboard. Volunteering to maintain the map, turn order list, quote collection, records of enemy hit points, etc. was like taking notes but even more helpful. I got to stand and move around and directly interact with what other players were saying.


• 
  Making notes about what I want to do next as soon as my turn is over. In combat, this looks like "if pirate A is still alive -> attack him with my axe again, otherwise -> investigate the body." Outside of combat it might look something like "Things I want to do: ask the shopkeeper about the rumors of dragons, look more closely at the pattern of cobblestones in the street, find the best dog in the market and pet it." My list will grow or shrink as I do things and more interesting things come up, but it helps me keep from forgetting what I wanted to do before my next turn comes around.

And some other stuff that has helped other ADHD players:

• Talking to the GM A good GM should help the group set ground rules and expectations before any play happens. A good player pays attention to which of those rules work for them and which rules (or circumstances) are interfering with their ability to play, and brings up concerns before they become problems. When I GM, I make a point to check in with all my players frequently, but especially players that seem distracted or like they might not be having a fun time. Together we can come up with solutions that work for the specific group. However, some GMs might wait for a player to come to them or might mistake distraction for a lack of interest. It's always a good idea to talk to your GM about your worries and struggles and see what they have to say. At the very least, it will reassure them that your behavior is not a reflection of their skills.




• playing with fewer people might be difficult if you are already in a group, but I really recommend sticking to a group that has 2-3 other players, especially if you find yourself getting bored or having difficulty maintaining focus while waiting for your turn. For one, you won't have to worry about speaking over as many people, but also there just won't be as long to wait between turns.




• Asking for more structure can help a lot of people. I have a good friend who has hyperactive type, and she struggles with blurting out and talking over people when she gets excited (e.g., while playing games that she really likes). When I played in a game with her, we as a group solved the issue by establishing a permanent turn order for all situations, that the GM enforced. In any specific scenario, we all got at one planning turn where we could voice our opinions/plans, before actually taking those actions, again in turn. The duration of a player's "turn" was flexible out of combat, and might be a single roll or a mini-scene. But the idea was that everyone should only speak when their turn is up, but waiting won't hurt because they will get their turn.




• Asking for more visuals like a map or enemy list can help remind you what's going on if you do lose focus for a bit. If your turn comes around in combat and you aren't sure exactly what happened before, you could still refer to the map to see which enemy you might want to attack or which PC you might want to help.




• Asking for more stable cues like an established combat order can help by providing a stable stimulus for when you should "tune in" and when it's okay to move around or take a mental break. For example, maybe you always take your turn after a specific other player. When you hear their voice, you know that you should start figuring out what you're going to do on your turn. You could also ask that as each turn passes, the GM states whose turn it is and who is up next (e.g., "Jenna, it's your turn, and Paul is next... Okay, Paul, you're up, Steph is next...")

I hope this helps! Good luck!

As someone with direct experience, this may help, both in gaming and in your wider life as well.

Tell people, explicitly, that you have ADHD, and you might get distracted, talk to much, repeat myself, ask questions without thinking them through, or get stuck into things and unable to pull out of them.

Then say something like, "If I talk too much, or cut in or over anyone, please tell me, and cut over me if you have to. I won't take it badly, I know I don't always catch myself and it's not good for the game. So please - if you need to rein me in, just say so, I'll appreciate it."

I've been doing that for years, socially and in games, and it always works well.