Autism

ADHD and autism are thought to have about a 60-70% genetic overlap. You can have either one separately or both.

Current research suggest that it is more likely that you have AuDHD than standalone autism, though (again, about 60-70% of people on the autism spectrum are estimated to have ADHD as well). I have not yet seen an estimate of the ADHD vs AuDHD population, though, so I'm not sure if the same pattern (more likely to have the combination than just ADHD) applies.

As others have said, there's also some overlap in how the two conditions present and the challenges faced by an individual with either, even though the underlying mechanisms are different.

You'll know you are ADHD (in addition to autism) if you consult a doctor and get diagnosed (or not).

If you're seeing that one condition dictates you must have the other, I'd assume you're dealing with cognitive bias. There are plenty of people in the world who have one without the other and clearly no indication of the other.

No sense in being "worried about ADHD" just for the sake of it. If you have ADHD symptoms that are hindering you in life, get professional help. If you are not hindered by ADHD symptoms, stop worrying about it? I understand that might be hard if you are obsessing over it, just saying there is no point to it if you don't actually have the symptoms.

Autism and ADHD can be said to belong to the same spectrum, and it's common to have a little bit of both. We have two kids on the spectrum, where one has level 2 autism (and some ADHD) and the other has level 2 (medium-severe) ADHD (with some autism).

Since effects of ADHD can be mitigated with medicines, the important question for you would be if you feel that "ADHD traits/behavior" is making a negative impact in your life. If so, there's some use in bringing this up with your healthcare and see if you can get a diagnose. If not, don't worry about it. Everyone's more or less on the spectrum - it's whether we can cope in our daily lives that is important.

(Disclaimer: I'm not a psychologist specializing in diagnosing ADHD and autism - my wife is. Everything that's correct in this post comes from me paying attention to her. Everything that's wrong comes from me not having understood)

As others have mentioned, there are lots of genetic links between the two. So a lot of Autistic ppl would also have ADHD (as well as a bunch of other interesting neurodivergent traits), but it is definitely not guaranteed. I am actually such an example... I have diagnosed ASD lvl 1 & have some ADHD-esque traits, but I do not meet the diagnostic criteria & thus do not have ADHD

To add to this discussion... unfortunately there aren't good ways to tell if one has ADHD except for consulting a psychiatrist. It's probably a good idea to not rely on self-diagnosis too, since ADHD does have medical interventions, but a good number of them are controlled substances and probably realllly shouldn't be taken by just about anyone

My hope is... I think most psychiatrists know the strong relations, so hopefully a good psych would have at the minimum also checked for ADHD while diagnosing for Autism...? Although to be honest, my first psych didn't do it either. I later went for a separate comprehensive psych eval for ADHD+others, which did just about everything under the sun... (ASD, ADHD, anxiety, IQ, psychopathy, aphantasia, alexythymia, reaction speed, ...)

Both are independ labels for a specific set of neurodivergent features your brain may or may not have.

Basically, a young brain grows and develops neurological connections. For most people, those connections are relatively similar or typical but minor differences in them is part od why people are all still unique.

When you are “blessed” with neurodivergent dna from your parents, you are more likely to make different, atypical connections.

There is biologically no difference between neurodivergence from autism or adhd. But for medical purposes we group an area of “symptoms” with a label so we can grant each the professional help they need.

Neurodivergence also does not even need to occur with a genetic predisposition, simply growing up differently to your peers can already show the difference, but it doesn’t need to be negative either. Just like how many parts of adhd and autism can be positive.

Autism and ADHD are both conditions that effects lots of different parts of thinking and interacting with the world. In some ways they are very different, with quite opposing outcomes (people with ADHD often seek novelty and struggle with repetitive task, while people with Autism can find security in repeated activities) but also with a lot of overlap (such as problems with executive function, social interactions, etc.)

Because of some of the overlap, it isn't always easy to identify what is causing a problem, but usually if you explore the reasons behind the problem or becomes clearer. Are you struggling to start an important task? Is it because you literally cannot make yourself, even though you're really stressed and worried, and you're just sitting there looking at the computer? Or are you struggling to start because you don't know all the information you need to make a key decision, and you know that you need to, but both choices are equally balanced and it's impossible to just choose?

The finally, there is a moderate amount of people who are AuDHD, and diagnosed with both. They report very conflicted needs, a desire for novelty but finding changes exhausting, needing a routine but getting bored of it easily. If you're already diagnosed with ASD, you could read some stuff about AuDHD and see of any of it sounds relevant. But if it does, you really need to see a professional about an actual diagnosis, because it is not easy to decide what is autism and what could be ADHD. But on the plus side, treatment for ADHD is really and very effective for most people, so you might actually be able to get some help of that is a source of real problems for you.

It’s not known yet how they are connected, even though the seem to team up sometimes. There is a test called ASRS. It’s a relatively reliable selftest to find out if a professional testing could be recommended.