I can spend nine hours on something without eating.
The problem is I do not get to pick what.

Concretely, this is the opposite of what most people picture when they hear "ADHD." The attention deficit is not a global lack of attention. It is a dysregulation. The ADHD attention dial swings from zero to ten with no gradient, and it sets itself on whatever is stimulating in the moment, regardless of what should be the priority.

When the topic is stimulating to my brain (strong interest, challenge, novelty, emotional urgency), the dial jumps to ten. And it stays there as long as the topic holds. That is hyperfocus. Not chosen concentration. Non-negotiable absorption.

Several authors distinguish hyperfocus from Csikszentmihalyi's flow. Flow is voluntary, controlled, exits naturally when the task ends. ADHD hyperfocus is involuntary, you do not decide when it begins or ends, and the exit is often brutal.

Phase 1: the hook. Something catches my attention. Often a technical detail. A problem that intrigues me. A blog post that asks an interesting question. At that moment, my brain switches over. The rest of the world goes blurry. I know there is an 80% chance I will spend the next several hours on this thing, even if I had other priorities.

Phase 2: immersion. Time disappears. I do not eat. I do not drink. I do not answer messages. If someone speaks to me, I hear them as if through glass. My brain runs at full speed on the subject. This is the most productive phase of my days. It is also the phase where I become unreachable, which is a problem when I am in a relationship or on a team.

Phase 3: saturation. Eventually the brain stalls. Not because I am done. Because it is done. Quality drops, I start making mistakes. This is when I should stop, but it is also when I cannot, because exiting hyperfocus is as hard as entering it.

Phase 4: the crash. When I finally disengage, I often have a headache, I am irritable, disoriented. My mood drops. This is documented in research: Hupfeld reports that abrupt exits from hyperfocus are linked to mood and productivity drops in the hours that follow. It took me years to connect my super-productive days to feeling low the next day.

The strongest explanation today goes through the dopaminergic system. The ADHD brain has a different activation threshold: a stimulus has to be stronger than usual to trigger the motivation circuit. A bland administrative task does not hit it. An intriguing intellectual problem triggers an outsized dopaminergic response. Once that circuit is on, it self-sustains. Volkow et al. documented this across several brain imaging studies (notably Volkow et al., 2009, JAMA).

Russell Barkley sees it from a complementary angle. For him, the ADHD brain has a deficit in inhibition and switching. Neurotypical attention shifts between tasks through continuous micro-switches. ADHD attention either hooks in or it does not. Once it hooks in, it cannot disengage easily.

Both mechanisms compound. Strong dopaminergic stimulus + difficulty disengaging = hyperfocus. That is also why stimulant medications (methylphenidate, lisdexamfetamine), which adjust dopamine availability, can dampen extreme hyperfocus while improving sustained attention on less stimulating tasks. My four months on Ritalin had that effect: less extreme hyperfocus, more capacity to finish boring stuff.

Recognise the conditions that trigger it. For me: a new problem, light time pressure, few competing stimuli, an object of interest tied to a strong topic (neuroscience, code, writing). I cannot trigger it, but I know when it is likely to come. On days when I need to make progress on something big, I deliberately set up the conditions and see.

Align my work with where it actually fires. I stopped fighting my brain to do administrative tasks that should take an hour and end up taking six. Instead, I cluster those tasks on dedicated days (where I know I will not get anything else useful done) and leave the "brain on" days for deep work. The productivity gap between the two types of days is huge.

Set physical guardrails. A water bottle next to me before I start. An alarm at noon to eat. A message to my close ones: "I will be unreachable for three hours, it is not about you." It sounds silly. But getting up to fetch water during hyperfocus means coming out of it. So I do not come out.

Document at the exit. When I come out of a session, I quickly note what I understood or produced, because I know that in two hours I will not be able to reconstruct the full context. The ADHD brain does not memorise the path, only the arrival.

The main trap is that hyperfocus locks onto what is stimulating, not what is useful. You can spend six hours perfecting a project's CSS palette while what was due tomorrow is a critical feature your brain finds boring. By end of day, you are exhausted, you have worked, and you have made zero progress on what mattered. That is one of the major frustrations of ADHD at work.

The second trap is the impact on relationships. When I am in hyperfocus, I am not unkind. I am just not there. My close ones took time to understand that my silences are not disinterest. They are neurological disengagements. But it is hard to accept when you are on the receiving end. A partner who asks how your day went and gets a depopulated "hmm" eventually feels invisible. Rightly.

The third trap is post-hyperfocus exhaustion. The phase 4 I described earlier. I confused it with mild depression for years. I told myself my mood swung. In fact, my "grey" days were almost always the days after a big hyperfocus session. Tracking that has been one of the most useful insights for understanding my mood.

I still cannot trigger it on demand. When urgent boring work lands on my desk, hyperfocus stays silent. I can force the start, I cannot force the absorption. That is why medication is still a relevant option when professional life demands more predictability than my brain alone can offer.

I cannot stop on time either. My only strategy that sort of works is the external alarm, and even then: 30% of the time I ignore it. What works better is when another person walks into the room. But I do not live in permanent supervision, so I lose.

And I have not found a reliable way to shorten the post-hyperfocus crash. Naps, walks, water, food, none of them really cut the crash phase short. The only thing that helps is to expect it and ask nothing of myself the day after.