[Symptom variations in ADHD: importance of context, development and comorbidity]

Attention-deficit hyperactivity (ADHD) is a common disorder in school-aged children and is associated with significant impairment in social and academic functioning. Its recognition is based on congruent information from different sources, because most ADHD children and adolescents are not completely aware of impairments caused by inattention and/or hyperactivity/impulsivity. Fluctuations in symptom expression may complicate the diagnosis: during clinical examination or tests sessions, ADHD symptoms may be less severe than usual or completely absent. This review examines variations in ADHD symptoms due to environmental context, internal state, circadian factors, development, psychiatric comorbidity and discusses their clinical relevance. Generally, ADHD symptoms are pervasive and identified in different areas of functioning. Despite their chronicity, they show a relative context-dependency. An unfamiliar environment or situation may lessen symptoms. The same happens in dual relations or in calm settings, when the child receives attention and positive reinforcement from the adult. On the contrary, the classroom situation with its high stimulation level (noise, visual distractors, large class size) is likely to reveal or accentuate instability, impulsivity and inattention. Independently from objective symptom fluctuations, the impact of ADHD symptoms, and their consequences on self-esteem may also vary with the degree of environmental mismatch. Recent research in experimental psychology also draws attention to the motivational state of ADHD children: preference for immediate gratification and delay aversion may explain why most of them show satisfactory attentional capacities in certain activities (for instance video games or TV), while showing impairment in school work or in other effortful tasks. The diagnosis of the full ADHD syndrome requires significant impact on functioning in at least two areas. Some children with "situational" ADHD are impaired either in school setting or exclusively at home. Manuzza et al. report long-term outcome of "situational" versus "pervasive" ADHD. School-ADHD, in opposition to home-ADHD shows similarities with the full blown syndrome, as regards proportion of anti-social personality disorder, psycho-social functioning and academic/professional achievements. Moderate seasonal variations have also been identified with less ADHD symptoms in August. This result is likely to reflect a better fit between individual characteristics and environmental demands during school holidays rather than neurobiological changes, as there are no convincing arguments for seasonal fluctuations of serotoninergic tone in ADHD. Another cause for variations in ADHD symptom expression may be the co-occurrence of a mood disorder. Relationships between early-onset mania and ADHD are discussed. The appropriate definition of prepubertal mania is still in debate; its recognition is hindered by symptom overlap and high level of comorbid conditions. Chronic emotional dysregulation with irritability and frequent temper tantrums, sometimes viewed as characteristics of early-onset mania, might reflect a--possibly severe--sub-type of ADHD rather than a prodrome of bipolarity. A marked cyclicity of symptoms, with periodic accentuation of ADHD and mood symptoms, requires careful monitoring and systematic analysis of comorbid conditions. Clarification of the complex interrelations between ADHD and bipolar disorder will be obtained from long-term studies.