Rodent research of attention-deficit/hyperactivity disorder: insights into widely used animal models

Abstract

Numerous rodent research models of attention-deficit/hyperactivity disorder (ADHD) have been proposed, including pharmacological, environmental, and genetically generated models. A rodent model for studying ADHD should demonstrate similarities to the disorder by mimicking its three core symptoms (face validity), should align with a theoretically justified pathophysiological basis (construct validity), and should provide insights into unknown aspects of ADHD neurobiology while offering potential new treatments (predictive validity). This review provides an overview of rodent research models, which vary in their pathophysiological alterations, ability to replicate behavioural symptoms, and response to pharmacological treatments. Given this heterogeneity, it remains challenging to determine which rodent model best represents ADHD or its different subtypes. Consequently, validating these models against contemporary medication therapies and testing candidate natural compounds as potential adjuvant treatments is essential. Additionally, combining models induced by neurotoxins, environmental substances, and genetic modifications may help evaluate potential interactions and their impact on ADHD development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42826-025-00255-5.

Background

Inattentiveness, hyperactivity, and impulsivity are the key characteristics and clinical symptoms of attention-deficit/hyperactivity disorder (ADHD), the most common neuropsychiatric disorder, with 8% to 12% of children in the United States diagnosed [1–4]. Currently, ADHD has a global prevalence of 8.0% in children and adolescents, while its prevalence in adults is 2.5% [5]. In addition, children and adolescents with ADHD face an increased risk of multimorbidity, as well as a range of behavioural, psychiatric (e.g., depression, drug abuse, and delinquency), and somatic (e.g., asthma and obesity) health issues [6–9]. The standard treatment for ADHD is pharmacotherapy, although psychotherapy, behavioural training, and psychoeducational interventions are also commonly used. The most effective approach often involves a combination of these treatments [2, 10–12]. Currently, ADHD pharmacotherapy consists of psychostimulants such as methylphenidate (MPH) and non-psychostimulants like atomoxetine (ATX), as well as other treatments involving glutamatergic agents [13].

Several studies have provided evidence of abnormalities in dopaminergic neurotransmission in ADHD [14–16], suggesting that these abnormalities are associated with the disorder’s pathophysiology [17–19]. Furthermore, research using animal models of ADHD has also demonstrated abnormalities in dopaminergic neurotransmission [20–22]. In addition, various findings suggest that oxidative stress and neuroinflammation are key pathophysiological factors contributing to the development of ADHD [1, 23].

Increasingly more genes are being identified as involved in the aetiology of ADHD, reinforcing that it is a highly heritable disorder, with an estimated heritability of approximately 76% [24, 25]. ADHD is highly polygenic, with approximately 7,000 genetic variants potentially explaining 90% of single-nucleotide polymorphism heritability, and common genetic variants associated with ADHD have been linked to impairments in attention and verbal reasoning [26]. Exposure to various environmental factors—such as pesticides, prematurity or low birth weight, maternal alcohol and tobacco use, maternal stress, nutritional deficiencies, obesity during pregnancy, and viral infections—has also been identified as contributing risk factors for ADHD [27–29].

Animal models

Rodents are widely used as experimental animal models to study various diseases, including diabetes, neurodegenerative disorders, and neuropsychiatric conditions [30–34], giving insights into the biomedical and evolutionary mechanisms of the nervous system, disease, and behaviour. Rodent models contribute to our understanding of the neuropathological, neurochemical, molecular, cellular, genetic, and environmental aspects observed in ADHD. These models of ADHD offer several advantages: they are less expensive to maintain, permit hypothesis testing by allowing control over genetic and environmental variables, enable the use of invasive methods not possible in humans, and provide better control over factors such as diet. Additionally, their physiology is relatively similar to that of humans (Fig. 1). These models can be useful for studying, the effects of various natural compounds or medications on different brain areas or specific tissues [35–37]. However, it should be noted that while rodent models can capture certain aspects of the human disorder, they do not always reflect the full heterogeneity of ADHD and do not fully account for the symptom variability observed across individual patients. Although rodents have simpler nervous systems, their basic behavioural mechanisms are similar to those of humans, and while it may be difficult, it is not impossible to study some complex cognitive behaviours [21]. Rodents do not exhibit human-like language, but certain features of language can be studied in rats—particularly their ability to recognise and generalise rule-based auditory patterns. This suggest that rats can detect abstract structural patterns in sound sequences in a way that is similar to how humans process syntax in language [38]. Flexible decision-making in complex environments is a hallmark of intelligent behaviour, and using a combination of behavioural, computational, and electrophysiological methods, it has been shown that both rats and humans share conserved mechanisms of cognitive flexibility in such environments [39]. A deeper understanding of the translational value of rodent models—due to their similarities with human physiology and disease mechanisms—can help researchers advance insights that support the development of targeted therapies for neuropsychiatric disorders.

Fig. 1.

Core symptoms of ADHD and criteria for animal models. This figure summarises human ADHD alongside the three validation criteria—predictive, face, and construct validity—used to evaluate pharmacological, environmental, and genetic rodent models of the disorder. These models are valuable for studying specific molecular, genetic, and cellular mechanism associated with ADHD

Model criteria

A suitable rodent research model of ADHD must meet three criteria (Fig. 1). (1) the model must replicate the three core symptoms of the human disorder: inattention, hyperactivity, and impulsivity (face validity). Although reproducing core symptoms can enhance face validity, it is not a strict requirement for a model to be considered valid. (2) the model must align with a theoretically justified pathophysiological basis of the disorder (construct validity). Construct validity has not been achieved for ADHD because the aetiology of the disorder remains unknown. Even so, partial construct validity has been demonstrated through insights into some underlying mechanisms. (3) the model should predict novel or future aspects of neurobiology, genetics, treatment responses, and ADHD-related behaviour (predictive validity). Several comprehensive review articles discuss the validity criteria of various rodent models of ADHD [22, 35–37, 40–42]. Although construct validity is often regarded as the key form of validity, it is not an absolute requirement for a model to be considered valid or suitable. Some models rely primarily on face and/or predictive validity but still provide valuable insights into the disorder. This presents a challenge in many neuropsychiatric disorders, including ADHD, where neurobiology is not yet fully understood. ADHD is highly heterogeneous and has a multi-aetiological basis, making construct validity difficult to achieve. Consequently, many of the currently available models demonstrate at least some degree of face, construct, and predictive validity for one or more ADHD symptom subgroups. Rodent research models of ADHD are primarily classified into two categories: those induced using various substances (pharmacological and environmental) and those that are genetically induced. The most widely used rodent research models for ADHD are summarised in Fig. 2.

Fig. 2.

Rodent research models of ADHD and their characteristic features. This figure summarises the various experimental rodent models of ADHD, including those induced with different substances (pharmacological and environmental) and genetic models. Each model highlights key behavioural and neurobiological characteristics relevant to ADHD. Further details are provided in the text

Pharmacological and environmental experimental rodent models of ADHD

Neonatal 6-hydroxydopamine-lesioned rodents

6-Hydroxydopamine (6-OHDA) has high affinity for the dopamine transporter (DAT) and norepinephrine transporter, allowing it to accumulate in both dopaminergic and noradrenergic neurons. Once inside the cell, 6-OHDA undergoes auto-oxidation, leading to the formation of reactive oxygen species. Additionally, 6-OHDA can inhibit mitochondrial complex I, generating hydrogen peroxide, superoxide, and hydroxyl radicals, ultimately resulting in adenosine triphosphate depletion [43–45]. The destruction of dopaminergic projections in the brains of neonatal 6-OHDA-lesioned rodents (rats and mice) leads to hyperactivity, impaired spatial discrimination learning, and changes in attention [46–53]. Impulsive-like behaviour has been observed in adult mice [47], and later studies demonstrated that 6-OHDA-lesioned mice also exhibited impulsivity-like behaviour during adolescence [46]. 6-OHDA-lesioned rodents, in combination with desipramine (to preserve noradrenergic neurons), represent the most widely used neurotoxin-based experimental model for studying ADHD. Many of the observed behavioural deficits are linked to acute adaptive alterations in the dopaminergic system caused by 6-OHDA lesions [22, 47]. These rodents exhibit decreased dopamine levels, reduced striatal DAT density, increased dopamine receptor D4 expression, and alterations in serotonin receptors [48, 50, 54–56]. Their behavioural deficits can be improved with treatment using psychostimulants or ATX [47–49, 57–59]. To evaluate the effects and mechanisms of neonatal 6-OHDA-lesioned rodents as an experimental ADHD model, three routes of administration have been used: intracisternal injection [57, 59], injection into the lateral ventricle [46, 47], and unilateral intrastriatal injection [52, 53, 60, 61]. Intrastriatal lesions can lead to the progressive loss of dopaminergic neurons in the substantia nigra pars compacta, resulting in dopamine depletion [53, 60, 61]. However, the route of 6-OHDA administration may influence outcomes and treatment responses. These rodent models demonstrate predictive validity, as psychostimulant and ATX treatments reduce hyperactivity and attention deficits. Construct validity is supported by changes in the dopaminergic and serotonergic systems, while face validity is established by the observed behavioural deficits observed. Thus, this model could serve as a reliable tool for studying ADHD. The characteristic features of pharmacological and environmental experimental models of ADHD are summarised in Table 1.

Table 1.

Features of pharmacological and environmental experimental rodent models of ADHD

Model	Face Validity	Predictive Validity	Construct Validity	References
Neonatal 6-OHDA lesioned rodents	Inattention Hyperactivity Impulsivity	Hyperactivity and inattention improved by amphetamines, MPH, and ATX	Dopaminergic and serotonergic modifications	[47, 53, 59]
Prenatal nicotine exposure	Inattention Hyperactivity Impulsivity	Hyperactivity improved by MPH	Dopaminergic modifications	[62, 63]
Prenatal ethanol exposure	Inattention Hyperactivity Impulsivity	Dopaminergic modifications improved by MPH and amphetamines	Dopaminergic modifications	[64, 65]
Heavy metal exposure	Hyperactivity No data regarding inattention No data regarding impulsivity	Hyperactivity improved by amphetamines and MPH	Dopaminergic modifications	[66, 67]
Neonatal hypoxia	Hyperactivity No data regarding inattention No data regarding impulsivity	Hyperactivity improved by amphetamines	Catecholaminergic and serotonergic modifications	[68]
Cerebellar lesion	Hyperactivity No data regarding inattention No data regarding impulsivity	No predictive validity data	No data regarding modifications of catecholaminergic system	[69, 70]
Maternal stress	Hyperactivity Inattention Impulsivity	Hyperactivity improved by dopamine receptor antagonist	Dopaminergic modifications	[71, 72]

Prenatal nicotine exposure

Exposure to nicotine during the prenatal and postnatal stages is considered an environmental risk factor for ADHD. Children born to mothers who smoked cigarettes before, during, or immediately after pregnancy have a two-fold higher risk of developing ADHD [73, 74]. A mouse model of prenatal nicotine exposure via drinking water exhibited hyperactivity, decreased dopamine turnover in the frontal cortex, reduced cortical volume, and sensitivity to oral MPH treatment [62]. Similarly, adolescent rats prenatally exposed to nicotine also displayed hyperactivity [75]. In another study, nicotine administered to pregnant mice through drinking water induced hyperactivity that was transmitted across generations, although only the founder generation was directly exposed. Notably, this transmission occurred exclusively via the maternal lineage [76]. Prenatal nicotine exposure through drinking water has also been shown to produce impulsive behaviours in rats and disrupt neural activity in the medial prefrontal cortex [63]. Additionally, in mice, nicotine exposure through drinking water resulted in significant deficits in attention and working memory in male offspring, but not in females [77]. However, because nicotine was administered via drinking water rather than through smoking boxes, this model could be considered more of a pharmacological rather than an environmental model. Variations in behavioural findings from these animal models are likely due to differences in routes of administration, doses, species, and timing of exposure. Despite this variability, prenatal nicotine exposure models have demonstrated face validity (behavioural deficits observed), construct validity (dopaminergic modifications), and predictive validity (hyperactivity improved by MPH treatment) in relation to ADHD.

Prenatal ethanol exposure

Drinking alcohol at any stage of pregnancy has been associated with an increased risk of ADHD in infants [78, 79]. Prenatal ethanol exposure in rats leads to neurochemical and morphological deficits in the brain, resulting in postnatal hyperactivity, impulsivity, and attention deficits [64, 65, 80]. Rats prenatally exposed to ethanol exhibit dysregulation of dopaminergic neurons in the ventral tegmental area, a dysfunction that can be regulated by MPH and amphetamines [81–84]. These findings support the presence of predictive validity (response to MPH and amphetamines), face validity (inattention, hyperactivity and impulsivity), and construct validity (dopaminergic modifications) in this model. While prenatal ethanol exposure is a recognised risk factor for ADHD, behavioural findings from animal model remain varied. Further research is needed to fully validate prenatal ethanol exposure as a reliable model for ADHD.

Heavy metal exposure

Excessive exposure to heavy metals is detrimental to neurodevelopmental processes, exerting neurotoxic effects that can impair cognitive functions. This has led to the implication of heavy metal exposure in susceptibility to ADHD [85]. Lead exposure during early development has been shown to induce hyperactivity in mice, an effect that was prevented with MPH and amphetamine treatment [66, 86, 87]. In rats chronically exposed to lead, dopamine turnover was found to be decreased in the striatum and nucleus accumbens [88]. Similarly, exposure to cadmium and manganese produced hyperactivity, spatial learning, and memory deficits in rats, effects that were associated with altered dopamine receptor and DAT levels [67, 89, 90]. While these experimental models only demonstrate elements of predictive validity (hyperactivity prevented by MPH and amphetamines), face validity (hyperactivity), and construct validity (dopaminergic modifications), further research is needed to fully establish their relevance as models of ADHD.

Neonatal hypoxia

Prenatal and perinatal brain hypoxia leads to behavioural and neurochemical changes, increasing the neurodevelopmental risk for ADHD [91]. Hypoxia induced by nitrogen in postnatal rats (90%–100% nitrogen exposure within 24 h of birth) has been shown to mimic the hyperactivity and learning impairments observed in ADHD [68, 92, 93]. These effects have been studied between postnatal days 2 and 10 [68, 94–97]. However, by 6–9 weeks of age, the hyperactivity was found to normalise [92, 94, 98], a characteristic observed in many individuals with ADHD after the teenage years. The hyperactivity was also alleviated with psychostimulant treatment [92]. Hypoxia induces age-dependent adaptive monoaminergic alterations. In the acute phase, there is a decrease in dopamine and norepinephrine levels in the cortex and striatum, while serotonin metabolite 5-hydroxyindoleacetic acid is increased in both the cerebellum and cortex [99]. Face validity is supported by the presence of hyperactivity, although further research is needed to evaluate attention deficits and impulsivity. Construct validity is linked to alterations in the catecholaminergic and serotonergic systems, while predictive validity is supported by the observed effect of amphetamines in reducing hyperactivity. Despite these findings, further research is required to fully determine the validity of hypoxia-induced models for ADHD.

Cerebellar lesions

The cerebellum has been found to be smaller in patients with ADHD, suggesting its involvement in the disorder’s development [100, 101]. While the cerebellum is primarily known for its role in coordination and motor learning, it is also involved in attentional control, working memory, emotion regulation, action planning, and response timing by processing input from various brain regions, the spinal cord, and sensory receptors [102]. Lesions to the cerebellum—induced using substances such as methylazoxymethanol, alpha-difluoromethylornithine, and dexamethasone—within 5–12 days post-birth result in cerebellar growth inhibition and the development of hyperactivity in rats [69, 70, 103, 104]. However, amphetamine treatment increased hyperactivity rather than alleviating it [103]. Face validity is partially supported because the lesions induce hyperactivity. Predictive validity is absent, given that amphetamine treatment exacerbates rather than reduces hyperactivity. Construct validity is difficult to determine due the lack of data on alterations in the catecholaminergic system in this model. Although current findings are insufficient to validate cerebellar lesions in rats as an ADHD model, this approach may provide valuable insights into the role of the cerebellum in ADHD pathophysiology. Further research is needed to establish its relevance as an experimental model.

Maternal stress

There is some evidence that prenatal maternal stress may be a risk factor for ADHD [105]. In maternally stressed mice, adult offspring exhibited hyperactivity and alterations in the midbrain dopaminergic system; however, administration of a dopamine receptor antagonist reduced hyperactivity [71]. Additionally, maternal stress-induced ADHD-like behavioural phenotypes in mouse offspring were linked to changes in plasma gamma aminobutyric acid (GABA) metabolism and dopamine concentration [106]. Cortisol is a key biological factor associated with stress-induced psychiatric disorders. Prenatal exposure to high corticosterone has been shown to induce ADHD-like behaviours—including impulsivity, hyperactivity, and inattention—as well as cognitive deficits such as learning and memory impairments. These effects are mediated through developmental delays in hippocampal CA1 neurons in rats [72, 107]. This experimental model demonstrates elements of face validity (inattention, hyperactivity, and impulsivity), predictive validity (hyperactivity reduced by dopamine receptor antagonists), and construct validity (dopaminergic modifications). However, further research is needed to fully establish its reliability as an ADHD model.

Genetic experimental models of ADHD

The spontaneously hypertensive rat

The spontaneously hypertensive rat (SHR) is the most extensively studied genetic rat model of ADHD. Developed in the 1960 s [108] through inbreeding of the normotensive Wistar–Kyoto strain, the SHR was originally bred for hypertension, although hypertension has not been reported as a characteristic of ADHD in humans. Despite this, SHRs exhibit high spontaneous motor activity and display all of the core behavioural characteristics of ADHD, including impulsivity, hyperactivity, poor sustained attention, and poor stability of performance when compared with Wistar–Kyoto rats [109–112]. Thus, face validity is supported by behavioural similarities to ADHD, construct validity is reinforced by alterations in the catecholaminergic system, and predictive validity is demonstrated by the efficacy of monoaminergic drugs in reducing ADHD-like behaviours [109, 113, 114]. However, the presence of hypertension in SHRs cannot be overlooked because increased blood pressure may influence behaviour, potentially confounding ADHD-related findings. A recent study also suggests that SHRs might not be a suitable model for the inattentive or combined subtypes of ADHD [115]. Face validity is supported by hyperactivity, impulsivity, and poor attention; the predictive validity is supported by the improvement with monoaminergic drugs; and construct validity is supported by data on catecholaminergic system alterations. Additional research is needed to determine whether behavioural deficits in SHRs are a direct reflection of ADHD-like pathology or a secondary effect of hypertension-induced brain alterations. Further investigation is also needed to explore the role of the SHRs as an ADHD model through alternative approaches. The characteristic features of genetic experimental models of ADHD are summarised in Table 2.

Table 2.

Features of genetic experimental rodent models of ADHD

Model	Face Validity	Predictive Validity	Construct Validity	References
SHR rat	Poor attention Hyperactivity Impulsivity	Symptoms improved by monoaminergic drugs	Catecholaminergic modifications	[108, 110, 111]
DAT-KO mouse	Inattention Hyperactivity Impulsivity	Symptoms improved by MPH	Dopaminergic modifications	[116, 117]
CM mouse	Inattention Hyperactivity Impulsivity	Hyperactivity improved by amphetamines	Catecholaminergic modifications	[118–120]
TRβ−1 mutant mouse	Inattention Hyperactivity Impulsivity	Hyperactivity improved by MPH	Dopaminergic modifications	[121, 122]
NK1R-KO mouse	Inattention Hyperactivity Impulsivity	Hyperactivity improved by amphetamines and MPH Impulsivity improved by ATX	Catecholaminergic and serotonergic modifications	[123, 124]

The DAT knockout mouse

The DAT knockout (DAT-KO) mouse is one of the most extensively characterised transgenic experimental models for ADHD. This model lacks the DAT due to deletion of the Slc6a3 gene, which encodes the DAT protein responsible for dopamine reuptake into presynaptic terminals [125–127]. DAT-KO mice exhibit ADHD-like symptoms along with alterations in spatial memory [116, 117]. MPH treatment ameliorates their hyperactive, inattentive, and impulsive-like behaviours [116]. The hyperactivity observed in DAT-KO mice is linked to a significant reduction in dopamine clearance [128]. As a result, extracellular dopamine levels in the brain are increased approximately five-fold due to slow dopamine clearance [125]. Face validity is supported by behavioural similarities to ADHD, construct validity is reinforced by alterations in the catecholaminergic system, and predictive validity is demonstrated by the efficacy of MPH in reducing ADHD-like behaviours. However, findings regarding DAT levels in patients with ADHD are inconsistent. Some studies have revealed increased DAT levels in the striatum of both children and adults with ADHD [56, 129, 130], whereas others have found reduced DAT expression in patients with ADHD using brain imaging studies [131]. To fully validate the DAT-KO model, further research is needed to clarify the role of DAT in ADHD pathophysiology and resolve these discrepancies.

The coloboma mutant mouse

The coloboma mutant (CM) mouse was developed through neutron irradiation, which induced a mutation on chromosome 2, disrupting several genes, including synaptosomal-associated protein 25 kDa (SNAP-25). The behavioural deficits observed in CM mice are associated with SNAP-25 dysfunction [120, 132, 133]. SNAP-25 is a crucial protein for neurotransmitter release because it facilitates the fusion of neurotransmitter vesicles with the presynaptic membrane. Due to this mutation, dopamine release in the striatum of CM mice is almost entirely absent [118]. CM mice exhibit behavioural deficits including impulsivity, spontaneous hyperactivity, impaired inhibition in a delayed reinforcement task, and delayed neurodevelopment [119, 120, 133]. Construct validity is supported by alterations in catecholaminergic systems—specifically, an increase in the noradrenergic activity and a decrease in the dopaminergic function. Face validity is assumed based on the presence of behavioural deficits resembling ADHD symptoms. Predictive validity is suggested by the effectiveness of psychostimulants in modulating ADHD-like behaviours. These characteristics indicate that the CM mouse may serve as a useful genetic model for studying ADHD; however, further research is needed to fully validate its applicability.

The thyroid receptor β−1 mutant mouse

The thyroid receptor β−1 (TRβ−1) mutant mouse is an animal model used to study ADHD. This mouse carries a mutant human thyroid hormone receptor β gene, derived from a patient diagnosed with resistance to thyroid hormone [121]. The disease is heritable and characterised by elevated levels of thyroid hormone and thyroxine, sometimes with elevated thyroid-stimulating hormone, tachycardia, and hearing loss [134]. Approximately 70% of children with this condition are diagnosed with ADHD [135, 136]. The TRβ−1 mutant mouse exhibits impulsivity, hyperactivity, and inattention, with elevated thyroid-stimulating hormone levels observed at 33 days of age. The behavioural deficits persist into adulthood [121, 122, 137]. Moreover, these deficits are related to the catecholaminergic system, as the mice show sensitivity to MPH treatment and display elevated dopamine turnover [121]. Nevertheless, the role of the thyroid system in ADHD remains unclear, suggesting that modifications in thyroid function could lead to alterations in brain development, resulting in ADHD-like behavioural phenotypes [138]. The TRβ−1 mutant mouse demonstrates face validity, as it exhibits all three core symptoms of ADHD. Predictive validity is supported by sensitivity to MPH treatment, while construct validity is indicated by alterations in the catecholaminergic system and evidence of developmental disturbances. While this model provides insights into the potential involvement of the thyroid system in ADHD, further studies are needed to establish its validity more conclusively.

The neurokinin-1 receptor knockout mouse

The neurokinin-1 receptor knockout (NK1R-KO) mouse, also known as the tachykinin receptor-1 knockout mouse, has been proposed as an experimental model of ADHD [124, 139, 140]. NK1 receptors are G-protein-coupled receptors activated by the binding of substance P and are expressed in the brain [124]. As a tachykinin neuropeptide, substance P is localised in brain regions involved in cognitive performance, motor control, and mood regulation. The NK1R-KO mouse exhibits locomotor hyperactivity in various experimental environments [123, 141, 142]. Later studies demonstrated that this mouse model also displays inattentive and impulsive-like behaviours, further supporting its relevance to ADHD. Given that it exhibits the core behavioural symptoms of the disorder, the NK1R-KO mouse demonstrates strong face validity as an animal model. The behavioural abnormalities in NK1R-KO mice are ameliorated by MPH, amphetamines, and ATX, indicating predictive validity [123, 143–146]. Additionally, findings suggest that NK1R-KO mice show alterations in catecholaminergic and serotonergic systems, further supporting construct validity [141, 147].

Conclusions

The criteria for validating rodent research models of ADHD depend, among other factors, on the behavioural alterations they display, including inattention, hyperactivity, and impulsivity, as well as the pathophysiological basis of the disorder, altered gene expression (given the highly polygenic predisposition to ADHD), and their response to medications. At present, validation of experimental rodent models remains incomplete. However, each model has its own strengths and weaknesses, contributing to a better understanding of different aspects of ADHD. Because many rodent models have not been thoroughly examined for inattention, impulsivity, and cognitive deficits, there is a pressing need for better pharmacological characterisation. Additionally, the genes implicated in ADHD, given its highly polygenic and heterogeneous nature, are often not adequately considered in many experimental rodent models, nor are the different subtypes of ADHD. Genetic models can serve as important tools to study disruptions in specific physiological pathways, such as those seen in certain knockout models, although these disturbances are not necessarily exclusive to ADHD; other disorders may exhibit similar alterations. While face validity and predictive validity can be more readily assessed, construct validity remains difficult to establish. Therefore, careful examination of evidence from experimental animal models, in parallel with clinical studies in humans, is essential. Extensive validation of models that meet these criteria is necessary before forming a solid theory about the aetiology of ADHD, particularly because current knowledge of its neurobiology from human studies remains limited. This limitation arises from ADHD’s extreme heterogeneity, multiple aetiologies, and complex multifactorial phenotype. Although hyperactivity is a key characteristic, it is insufficient on its own to establish adequate face validity. Rodent models that present abnormalities not typically observed in patients with ADHD should also be critically evaluated—for example, the presence of hypertension in SHRs, which is not a defining feature of ADHD. However, it is important to note that SHRs do not develop hypertension until adulthood (10–12 weeks of age), whereas hyperactivity is observed earlier, during adolescence (3–4 weeks of age) [21, 148]. Currently, the validation of experimental models is primarily based on behavioural criteria (face validity), but there remains a poor understanding of ADHD’s construct validity. A key aspect of validation is the model’s responsiveness to ADHD medications (predictive validity), whether psychostimulants or non-psychostimulants. Among all the experimental rodent models discussed, only a few exhibit an adequate response to the psychostimulants commonly used to treat ADHD. Some models respond only to MPH or amphetamines alone, while others fail to respond to either treatment. Additionally, to achieve predictive validity, experimental models of ADHD must also be assessed for their response to ATX, a widely used non-psychostimulant treatment. Therefore, further rigorous research is required to validate these models, ensuring that some can be assessed not only against current drug therapies but also in relation to potential alternative or co-adjuvant therapies. In summary, research models that demonstrate both face validity and predictive validity could be valuable for investigating contemporary ADHD drug therapies and testing candidate compounds suitable for adjuvant treatment. Future studies should focus on experimental animal models that capture the heterogeneous and multifactorial phenotype of ADHD. Moreover, genetic models, as well as those induced by neurotoxins or environmental substances, should be combined to evaluate potential interactions and assess their impact on ADHD development.

Abbreviations

6-OHDA

6-hydroxydopamine

ADHD

attention-deficit/hyperactivity disorder

ATX

atomoxetine

CM

coloboma mutant

DAT

dopamine transporter

DAT-KO

dopamine transporter knockout

MPH

methylphenidate

NK1R-KO

neurokinin-1 receptor knockout

SHR

spontaneously hypertensive rat

SNAP-25

synaptosomal-associated protein 25 kDa

TRβ-1

thyroid receptor β-1

Authors’ contributions

J.C.C. conceived the topic of the review article and was responsible for writing, editing, and finalising the manuscript. The author has read and approved the published version of the manuscript.

Funding

This research was funded by Fondos Federales (grant numbers HIM/2022/039 SSA-1804 and HIM/2021/022 SSA-1728).

Data availability

All data presented in the manuscript were collected through a literature search.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The author declares no conflicts of interest.