Trastorno por déficit de atención e hiperactividad

Complete Reference: Ruiz, F. J., Luciano, C., Gil González, E., & Barbero Rubio, A. (2012). Trastorno por déficit de atención e hiperactividad. In F. J. Quintero, J. Correas & F. J. Quintero (Eds.), Trastorno por déficit de atención e hiperactividad (TDAH) a lo largo de la vida (pp. 1-48). Barcelona: Masson.

Article Type: Book chapter—comprehensive theoretical and conceptual review

Central Thesis and Objectives

This chapter presents a comprehensive review of Attention Deficit Hyperactivity Disorder (ADHD) from a contextual-functional perspective grounded in Radical Behaviorism and Relational Frame Theory. The central thesis is that, although there exists scientific consensus that ADHD is a neuropsychiatric disorder of biological origin with predominant genetic influence, this conceptualization has generated important iatrogenic effects, especially in diagnostic evaluation and treatment. The authors propose that a contextual-functional analysis of the behavioral deficits and excesses characteristic of ADHD can provide a more complete vision that overcomes limitations of purely biologistic models. The objective is to integrate historical, epidemiological, etiological, and treatment evidence under an analytical-functional framework that recognizes the importance of verbal processes and self-regulation in the genesis and maintenance of ADHD.

Theoretical Framework

The theoretical framework integrates multiple perspectives under the umbrella of Radical Behaviorism (Skinner, 1953). The authors structure their analysis around five dimensions: (1) historical evolution of the ADHD concept from early conceptualizations of minimal brain damage (Still, 1902) to modern concepts of attention deficit; (2) diagnostic criteria according to DSM-IV-TR and ICD-10; (3) epidemiological data, comorbidity and prognosis; (4) etiology from genetic, neurobiological and environmental perspectives; and (5) empirically validated treatment approaches. Crucially, the contextual-functional approach recognizes that behavior characteristic of individuals diagnosed with ADHD is caused by lack of opportunities for appropriate discrimination and reinforcement to establish adequate stimulus control and behavioral inhibition. Barkley's hybrid model of self-regulation (1990, 1997, 2006) is presented with acknowledgment of its influence but also with substantial critiques regarding its reductive neurobiological assumptions.

Argument Development

The argument unfolds through multiple sequential movements:

Section 1: Brief Historical Overview of ADHD

The authors document how ADHD has evolved from descriptions of hyperkinetic behavior in the nineteenth century (Still, 1902) to inclusion in modern diagnostic classification systems. A crucial point is that many diagnostic labels (minimal brain dysfunction, hyperkinetic syndrome of childhood, attention deficit disorder, hyperkinetic disorder) have varied with each revision of diagnostic manuals. The authors underscore that this variability reflects not so much advances in scientific understanding but changes in political and theoretical conceptualizations about what constitutes the "problem" of ADHD. During the 1970s, especially with Virginia Douglas, there was a paradigm shift: focus moved from hyperactivity to attention deficit as the central symptom.

Section 2: Diagnostic Criteria, Epidemiology, Comorbidity and Prognosis

The authors systematically review DSM-IV-TR and ICD-10 criteria, noting they require presence of 6 or more attention symptoms and/or hyperactivity/impulsivity. Three subtypes are established: combined, predominantly inattentive, and predominantly hyperactive/impulsive. An important controversy is noted: DSM-IV-TR criteria appear to be imposing themselves despite not being free from criticism, particularly regarding lack of etiological information about heterogeneity of individuals with the same ADHD subtype. Prevalence rates are documented as ranging between 3% and 7%, with considerable variability depending on whether more restrictive criteria (DSM) or broader criteria (ICD-10) are used.

An important epidemiological finding is that historically prevalence rates showed an approximately 4:1 ratio (male:female), although more recent data suggest this difference has been modulated. The authors note that ADHD has shown persistence into adulthood more robustly than initially expected, with 60-70% of childhood cases continuing to present symptoms in adolescence.

Section 3: Associated Problems, Comorbidity and Prognosis

ADHD is associated with a wide variety of problems spanning motor deficits, cognitive, academic, adaptation, and health risks. In the cognitive area, children with ADHD show intelligence test scores approximately 10 points below normal population. Difficulties in reading (8-39%), mathematics (12-33%), and writing (>60%) are frequent, with 30% requiring personal tutoring. Motor development shows delays in motor coordination (up to 52% of cases) and writing problems. Emotional development is characterized by poor emotional self-regulation, irritability, reduced frustration tolerance and reduced empathy.

Comorbidity is "the rule rather than the exception" with prevalence rates in clinical population of 75-90%. Most frequent comorbid diagnoses include Oppositional Defiant Disorder (ODD: 45-55%, up to 84% in clinical population) and Conduct Disorders (35-45%, almost always associated with ODD). In adolescence and adulthood, comorbidity with risky sexual activities (30-40% of adolescent pregnancies), transmission of sexually transmitted diseases, and traffic accidents is substantial.

Section 4: Etiology from Multiple Perspectives

Cerebral anatomy, cerebral functioning and neurochemistry of ADHD

The authors reverse the historical conceptualization of brain damage, noting that most children with ADHD have no detectable brain lesions. Nevertheless, there exist multiple structural differences at the group level: smaller frontal lobes, smaller basal ganglia volume, asymmetric cerebellar hemispheres. The authors emphasize that it is important to note that detection of structural differences does not mean these are causes of the main attention/behavioral problem of ADHD, but rather a component of a more complex picture.

Regarding brain functioning, diverse brain regions show reduced activation, including inferior central cortex, caudate nuclei, supplementary motor areas and temporo-parietal cortex. Interpretations of these findings remain controversial, especially regarding whether such differences precede or result from ADHD.

Neurochemistry emphasizes dopamine and noradrenaline in frontostriatal circuits. Stimulants improve activity in these circuits, although the exact mechanism remains unclear.

Genetics of ADHD

Twin studies show elevated ADHD incidence (81% in monozygotic vs. 29% in dizygotic), suggesting heritability of 75%. However, the authors voice substantial criticisms: molecular genetics studies have not identified specific genes explaining more than 1% of variance. This is presented as evidence that genetic studies should not be interpreted as evidence that attention problems result from genetic factors.

Influence of Environmental Factors

Prenatal and perinatal complications (low birth weight, hypoxia, anoxia, maternal prenatal stress, high lead exposure, tobacco/alcohol consumption during pregnancy) have been proposed as etiological factors, although evidence is inconclusive in many cases. The authors underscore that such physical events do not cause lack of attention to appropriate stimuli or lack of self-control skills.

Analytical-Functional Approach

The Radical Behaviorism perspective conceptualizes inattentive and impulsive behavior as product of the history of successive interactions of the organism with the environment. The historical context, joined to the present context, generates the functions to which the person responds at any given moment. Behavior characteristic of ADHD would be caused by lack of opportunities for discrimination and reinforcement to establish stimulus control and potentiation of self-control behaviors. In their history, there would have been multiple conditions where adults in the child's environment would have potentiated behaviors incompatible with paying attention to what is essential at each moment, persistence in tasks, and achievement of long-term objectives.

Barkley's Hybrid Model of Self-Regulation

Barkley's model proposes that ADHD results from motivational rather than attention deficit, related to delay in development of behavioral inhibition and self-control. The model proposes central nucleus in conduct inhibition deficit, operationalized as inability to inhibit immediate response, capacity to stop habitual response patterns permitting delay for decision-making, and capacity to protect such delay period against interference. Executive functions (internalization of publicly observable behaviors) would depend on ordered development of: (a) non-verbal working memory providing internalization of sensorimotor activities; (b) working memory understood as internalization of speech; (c) self-regulation of affect and motivation; and (d) reconstitution allowing organization and creation of new action strategies.

The authors acknowledge important acceptance of Barkley's model despite criticisms, principally regarding its structuralist assumptions. A primary limitation of the model is that, although it describes well the development of self-regulation, it does not specify what conditions are necessary for each of the components to emerge.

Section 5: Treatments

The authors review empirically validated treatments, dividing into: (a) pharmacological treatments (mainly methylphenidate), (b) behavioral treatments (contingency management), and (c) emergent treatments or under investigation (neurofeedback, physical exercise, self-instructional training, say-do correspondence training, Acceptance and Commitment Therapy, third-generation therapies).

Pharmacological Treatment

Methylphenidate is the most widely used pharmacological treatment, received by at least 2.8% of school-age children in the United States. Stimulants have demonstrated efficacy in all three ADHD subtypes, although response rate is lower in the inattentive subtype. In other age ranges, efficacy is lower. Most side effects are relatively mild (abdominal pain, headache, anorexia, insomnia), although can be substantial. The controversy regarding effect on growth has been widely discussed. A current generalized consensus is that psychopharmaceuticals do not "cure" ADHD and should be used in conjunction with psychological treatment.

Behavioral Treatments: Contingency Management

Parent behavioral training, consisting of teaching behavior modification techniques to educators, is considered an empirically established treatment. Contingency management in the classroom consists of instructing teachers in behavior modification techniques. There exist good numbers of studies comparing contingency management versus pharmacological treatment, with mixed results, although efficacy of contingency management is similar regardless of whether ADHD is accompanied by other disorders. However, substantial variability exists in maintenance and generalization of effects.

Emergent or Investigational Treatments

Neurofeedback, although labeled "possibly efficacious," shows limited evidence of efficacy. Physical exercise has shown utility as a reinforcer of desirable behaviors. Self-instructional training historically showed poor efficacy. Say-do correspondence training has shown promising results but requires more research. Recently, third-generation therapies including Acceptance and Commitment Therapy (ACT) have begun to show promise as interventions, particularly in adolescents and adults.

Implications

The implications of this contextual-functional analysis are substantial for clinical practice, research, and public policy:

For diagnosis: A contextual-functional analysis suggests that rather than relying exclusively on categorical symptom criteria, clinical evaluation should examine the antecedents and consequences controlling problem behaviors. This opens opportunities to "break down" diagnostic labels and analyze individual cases with greater precision.

For treatment: The growing recognition of the importance of verbal processes and self-regulation grounded in recent research on language and cognition from a contextual-functional perspective suggests that ADHD treatment can benefit from interventions oriented toward developing functional self-regulation repertoire, particularly potentiating creation of new self-rules or thoughts about the self that communicate that their attention or impulse problem is "outside" the person's control.

For public policy: The analysis suggests that overgeneralization of ADHD diagnosis with stimulants as reference treatment may be producing a series of important iatrogenic effects.

Significance and Contribution

The contribution of this chapter is multidimensional. First, it provides a rigorous synthesis of historical, epidemiological, and etiological literature on ADHD, enabling readers to familiarize themselves with current state of science. Second, it articulates substantial criticism of purely biologistic approaches, showing how such approaches can generate iatrogenesis when resulting in overadministration of diagnosis and medication in decontextualized manner. Third, it proposes an analytical-functional framework that potentially allows more complete understanding of ADHD etiology that integrates biological, genetic, environmental, and verbal factors. Fourth, it provides theoretical basis for development of behavioral interventions recognizing importance of self-regulation and verbal processes, suggesting future research may benefit from application of Relational Frame Theory principles to understanding and treatment of ADHD. Finally, the contextual-functional perspective raises important concerns regarding current practice of diagnosis and generalized pharmacological treatment of ADHD, especially in populations where the disorder may be less unequivocally identifiable or where behavioral interventions may be more appropriate.