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Daylight is the strongest synchronizer of human circadian rhythms. The circadian pathway hypothesis posits that synchrony between daylight and the circadian system relates to (in)attention. The dopamine neurotransmitter system is implicated in regulating the circadian system as well as in (attention)-deficit hyperactivity disorder [ADHD]. We studied the role of functional genetic variation in the gene encoding of dopamine-receptor-D4 (DRD4) in the relationship between inattention and seasonal daylight (changes). Gene-by-environment (GxE) mega-analyses were performed across eight studies including 3757 adult participants (with and without ADHD). We tested 1) theSpring-focus hypothesis, in which attention in 7R-carriers normalizes with increasing daylight levels preceding measurement, 2) theSummer-born ADHD hypothesis, in which 7R-carriers report more inattention when born in spring/summer than in autumn/winter, 3) theWinter-born ADHD hypothesis, opposing the second hypothesis. TheSpring-focus hypothesiswas upheld (1386 ADHD, 760 controls;d=-0.16 between periods); 7R-carriers reported evenlessinattention than 7R-non-carriers after winter solstice (d=0.27 between genotype-groups). Results were diagnosis-independent. Sensitivity analyses at individual study level confirmed the circannual patterns for 7R-carriers. Incorporating geographic changes into the independent measure, we also calculated changes in sunlight levels. This approach likewise showed that inattention correlated negatively with increasing light levels in 7R-carriers (r=-.135). Results emphasize peripheral effects of dopamine and the effects of (seasonal) daylight changes on cognition.

Objective: A circadian pathway has been proposed where artificial blue light exposure in the evening delays sleep onset, thereby reducing sleep duration, which, in turn, results in increased symptoms of inattention. Hyperactivity, on the other hand, may be part of a different pathway, where symptoms of disordered breathing in sleep (DBS) result in increased hyperactivity/impulsivity symptoms (DBS pathway). The current study aimed to investigate the separate components described within the proposed pathways. Method: Data from 143 children with ADHD from a multicenter study were available for DBS pathway analyses and a subset (N=114) for circadian pathway analyses. Results: Each hypothesized step of both pathways was in accordance with the data when analyzing teacher- but not parent-rated symptoms.Conclusion: Relationships within the circadian and DBS pathways that were previously established in separate studies using separate samples were now reproduced in one sample, albeit only for teacher-rated symptoms of primary school-aged children.

As the largest randomized clinical trial conducted by the National Institute of Mental Health, the Multimodal Treatment Study of Children with ADHD (MTA) will yield data on a diverse sample of 576 7.0- to 9.9-year-old children with attention-deficit hyperactivity disorder (ADHD), Combined type, regarding the relative and combined effectiveness of psychosocial and pharmacologic interventions. After delineating key challenges posed by such a multi-site investigation, we describe the MTA's multiple-gating procedures for recruitment, screening, and diagnosis of a diverse sample. We then discuss the cross-domain assessment battery for tracking the sample before, during, and after 14 months of active intervention. Throughout, we emphasize the guiding principles that shaped pertinent decision making. Highlighted are issues of psychometric adequacy; dimensional vs. categorical measurement; multi-method, multi-agent, and multi-domain coverage; plotting of individual trajectories of development and change; respondent bias and burden; appraisal of treatment processes as well as outcomes; and con struction of composite indices.

Although stress can aggravate attention-deficit/hyperactivity disorder (ADHD) symptoms, and stress disorders can sometimes mimic ADHD, ADHD is generally more a cause than an effect of stress. ADHD stresses the individual who has ADHD by handicapping achievement (both academic and occupational), peer and other social relations, self-esteem, and even physical safety. It stresses parents by complicating caregiving and supervision and by necessitating expensive and worrisome treatment. It stresses teachers by complicating teaching and stresses coaches, bus drivers, vice principals, and other school staff by the individual's failure to follow directions and need for greater disciplinary effort. It stresses classmates by classroom disruption and interference with their learning. In adulthood it stresses spouses by the individual's disorganization, poor money management, and restlessness; it stresses employers and coworkers by failure to follow directions or schedule; and it stresses peers by failed appointments and unreliability. The ripples of stress emanating from ADHD thus leave no one in our interdependent society unperturbed.

The twentieth-century increase in human height in affluent nations may not be entirely due only to such nurturant considerations as food supply and electric lights. A possible genetic role might be found in interactions of food supply, maternal pelvic size, and height-survival/vulnerability links, and in mate selection. Humans seem to be following the paleontological principle that most species tend to evolve larger sizes over time.