I am a Highly Sensitive Person (or HSP).
And I am an HSP with ADHD.
Lots of HSPs are afflicted with ADHD, but for several years now I have been pondering the overlaps and connections. Being an HSP is not a "diagnosis," it simply means you have an inborn genetic trait; your body is "hard wired" a certain way. You feel more; you feel more intensely.
It is really important to understand that being an HSP and having ADHD are two distinct situations. One does not CAUSE the other, and one does not IMPLY the other. To the degree there are correlations between the two, they are typically "non-causal."
Stated differently, I am having "the same ADHD experience" as everyone else, but because I am an HSP, how that feels is more intense than most people's feelings.
One of the places I have struggled most is to manage the "limited bandwidth/energy" I often have because I am highly sensitive alongside the general distractability that goes with ADHD. The end result is this "state" in which I feel overwhelmed and overstimulated (the "HSP part") by the fact that my inability to focus (the ADHD part) is keeping me from being able to efficiently navigate daily life.
In a practical sense, it has manifested as periods during which I feel totally immobilized... not by my actual work and chores, but by knowing how much effort it will take simply to stay focused.
the Inattentive form of ADHD (wikipedia), which is quite different from the well-known "Hyperactivity" form most people are familiar with.
I am still trying to make sense of the "intersect" of the two. Here's a metaphor that helps me a little:
I think of myself as a piece of machinery. I have a fuel tank containing a certain amount of fuel. As people, we all have "fuel tanks" of certain sizes. As a Highly Sensitive Person, I burn the available fuel faster than most people. As a result, when I am faced with the consequences of my ADHD, I have less fuel available to "fix things" and simply "keep plugging along," till whatever I needed to do is done. This leads to a "secondary feedback loop" in which I feel overwhelmed because it feels like no matter what, I won't have the fuel reserves to complete what I need to deal with.
Many years ago, I used to think of it as "Bailing out the Titanic with a tea cup." No matter what, the ship would "sink." My efforts were only sufficient to slow down the inevitable sinking.
Hence, a period of years during which I have been trying to "simplify" my life, so the "available fuel" will be sufficient to deal with the "stuff of life"... because there's no "increasing the size of the fuel tank." The answer, continuing with the ship metaphor, isn't to become better at bailing, but to make sure I'm on a smaller ship.
If you are an HSP with ADHD, "simplifying life" may be one of your single best coping tools-- and I also mention that because many HSPs are loath to resort to medications, because of the stronger impact of side effects.