The shortest version of this story: ADHD is too messy, varied, and biologically complicated for one lab animal to play the whole part. The interesting version takes a bit longer.

Scientists have spent years asking rats, mice, and the occasional zebrafish to help explain ADHD. Which is a fairly bold request. "Could you, small whiskered stranger, model a human condition involving attention, impulse control, development, genetics, environment, and a distressing relationship with unfinished tasks?" Best of luck to all involved.

That impossible brief is exactly why this new review matters. Bou Sader Nehme and colleagues pulled together the sprawling world of ADHD animal models and asked a simple but annoyingly necessary question: which models are actually good for what? Their answer is refreshingly unsentimental. No single model captures ADHD in full, because ADHD itself is not one neat, uniform disorder with a tidy little bow on top (Bou Sader Nehme et al., 2026).

ADHD is not one flavour of chaos

If you zoom out from the stereotypes, ADHD is not just "can't sit still" or "forgot where the keys are again." It involves different mixes of inattention, hyperactivity, impulsivity, executive dysfunction, altered reward processing, and often other conditions tagging along like unwanted plus-ones. Modern reviews describe ADHD as a developmental condition shaped by many genes and environmental factors, with brain differences spread across attention, control, timing, and reward networks (Faraone et al., 2024; Koirala et al., 2024).

That matters because animal models are judged on three big ideas: face validity, construct validity, and predictive validity. In plain English: does the animal resemble ADHD behaviourally, does the biology make sense, and does it help predict treatment effects? Lovely in theory. Slightly less lovely once real brains arrive and start behaving like overengineered Victorian plumbing.

Why one rat is not "the ADHD rat"

Some models are old favourites. The spontaneously hypertensive rat, or SHR, is probably the celebrity guest of ADHD animal work. It shows hyperactivity, impulsivity, and attention problems, which is handy. It also has hypertension, which is less handy when you're trying not to confuse cause with side quest. Other models tweak dopamine transporters, SNAP-25, or environmental exposures such as prenatal nicotine, each reproducing one slice of the ADHD picture and missing other slices. The field has known this for a while, but the new review says it plainly: treating one model as a stand-in for all ADHD is a category error in a tiny lab coat (Davids et al., 2022).

That point has become sharper recently. A newer perspective on next-generation models argues that the future is not just "find the right gene and make a mouse weird." It is gene-by-environment models, paired with better tests for timing, decision-making, and executive control - the parts of ADHD that still refuse to behave for current treatments (Fujita et al., 2025).

Why this matters outside the animal room

This is not academic housekeeping. Better models mean better odds of understanding why current ADHD medications help many people, help some only partly, and do not fix everything. Stimulants can work remarkably well, but they are not a magical "brain sorted" button. Symptoms vary. Side effects vary. People, in one of evolution's more exhausting habits, refuse to come in standard issue.

If researchers use the wrong animal model for the wrong question, they may end up studying a convincing imitation of the wrong problem. That slows drug discovery, muddies mechanism studies, and wastes years chasing findings that do not travel well from cage to clinic. The review's contribution is not glamorous, but it is useful in the way maps are useful when people keep walking into hedges. It gives researchers a more disciplined way to match model to question.

If that discipline sticks, the payoff could be substantial. More precise models could help separate ADHD subtypes, clarify which circuits drive inattention versus impulsivity, and support treatments aimed at cognitive control, motivation, or timing deficits rather than just broad symptom suppression. In other words, less "here is a stimulant, good luck" and more targeted care. Medicine occasionally enjoys specificity. One should encourage it.

The awkward, honest ending

Animal models are not miniature patients. They are tools. Good ones, sometimes brilliant ones, but still tools. This review lands because it resists the usual temptation to oversell. Instead of announcing that one mouse holds the secret to ADHD, it says something more useful: the disorder is diverse, so the models must be diverse too.

Which is less cinematic than a miracle breakthrough, certainly. But it is also how science tends to work when it is behaving itself.

References

1. Bou Sader Nehme S, Sánchez-Sarasúa S, Medrano MC, et al. Animal models of attention-deficit/hyperactivity disorder: Diversity and validity. Pharmacol Rev. 2026;78(1):100108. doi:10.1016/j.pharmr.2025.100108
2. Faraone SV, Bellgrove MA, Brikell I, et al. Attention-deficit/hyperactivity disorder. Nat Rev Dis Primers. 2024;10:11. doi:10.1038/s41572-024-00495-0
3. Koirala S, Grimsrud G, Mooney MA, et al. Neurobiology of attention-deficit hyperactivity disorder: historical challenges and emerging frontiers. Nat Rev Neurosci. 2024;25:759-775. doi:10.1038/s41583-024-00869-z
4. Davids LM, Petrovic P, Von Huben SN, et al. Review of rodent models of attention deficit hyperactivity disorder. Neurosci Biobehav Rev. 2022;132:621-637. doi:10.1016/j.neubiorev.2021.11.041
5. Fujita H, Hirano T, Hasegawa W, et al. Animal models for the study of ADHD: the need for next-generation models. Front Psychiatry. 2025;16:1773090. PMCID:PMC13056871

Disclaimer: The image accompanying this article is for illustrative purposes only and does not depict actual experimental results, data, or biological mechanisms.