The aim of this study was to conduct a systematic review of the literature and meta-analysis to estimate the association between psychophysiological activity and reactivity at baseline or after a psychological task with conduct problems (CP) among children and adolescents. We systematically reviewed published studies reporting autonomic nervous system activity in youth with CP and meta-analyzed the relationship between CP and autonomic baseline as well as task-related reactivity in 66 studies (N = 10,227). Across 34 included case-control studies that were based on CP cut-off scores, we found a significant pooled effect for task related Skin-Conductance, Respiratory Sinus Arrhythmia, and cardiac Pre-Ejection Period, but no significant group differences for Heart Rate nor for any baseline measures. Findings suggested reduced parasympathetic and sympathetic reactivity to emotional tasks, pointing to co-inhibition of the two systems. However, across 32 studies with correlational design we only found a significant negative correlation of baseline and task-related heart rate with CP. The present meta-analysis derived several conclusions that have the potential to inform biological vulnerability models and biologically driven interventions.

The patho-etiology of mental disorders with onset in childhood or adolescence remains largely unknown. We conducted an umbrella review of meta-analyses (MAs) on environmental factors associated with mental disorders with onset in childhood/adolescence. We searched Pubmed-MEDLINE/EMBASE/PsycInfo databases, last search April 29th, 2020. Quality of MAs was measured with AMSTAR-2. Out of 6851 initial references, ten articles met inclusion criteria, providing 23 associations between 12 potential environmental factors and nine disorders (cases: 8884; N = 3,660,670). While almost half of the associations were nominally significant, none of them met criteria from either convincing or highly suggestive evidence. A single association was supported by suggestive evidence (maternal exposure to lithium or antipsychotics with neuromotor deficits), but it was affected by confounding by indication. Ten more associations had weak evidence, and 12 associations were not statistically significant. Quality of meta-analyses was rated as high in two, moderate in one, low in four, critically low in two, and not pertinent in one (individual participant data). Methodologically-sound research is needed in this field.

A controversy exists on whether there is an over or underuse of medications for Attention-Deficit/Hyperactivity Disorder (ADHD). We conducted the first meta-analysis to estimate the rate of ADHD pharmacological treatment in both diagnosed and undiagnosed individuals. Based on a pre-registered protocol (CRD42018085233), we searched a broad set of electronic databases and grey literature. After screening 25,676 abstracts, we retained 36 studies including 104,305 subjects, from which 18 studies met our main analysis criteria. The pooled pharmacological treatment rates were 19.1 % and 0.9 % in school-age children/adolescents with and without ADHD, respectively. We estimated that for each individual using medication without a formal ADHD diagnosis, there are three patients with a formal diagnosis who might benefit from medication but do not receive it in the US. Our results indicate both overtreatment/misuse of medication in individuals without ADHD and pharmacological undertreatment in youths with the disorder. Our findings reinforce the need for public health policies improving education on ADHD and discussions on the benefits and limitations of ADHD medications.

There is a significant knowledge gap in research on Attention-Deficit/Hyperactivity Disorder (ADHD) in older adults. Via a systematic review and meta-analysis, we aimed to investigate the prevalence of ADHD in older adults, considering different assessment methods. We searched five electronic databases up to June 26, 2020. We identified 20 relevant studies with 32 datasets providing a total sample size of 20,999,871 individuals (41,420 individuals with ADHD). The pooled prevalence estimates differed significantly across assessment methods: 2.18 % (95 % CI = 1.51, 3.16) based on research diagnosis via validated scales, 0.23 % (0.12, 0.43) relying on clinical ADHD diagnosis, and 0.09 % (0.06, 0.15) based on ADHD treatment rates. Heterogeneity was significant across studies for all assessment methods. There is a considerable number of older adults with elevated levels of ADHD symptoms as determined via validated scales, and the prevalence of treated ADHD is less than half of the prevalence of clinically diagnosed ADHD. This highlights the need for increased awareness of ADHD clinical diagnosis and treatment in older adults.

Available meta-analyses point to a significant association between attention-deficit/hyperactivity disorder (ADHD) and obesity. The possible mechanisms underlying this relationship are unclear. Here, we overview the studies aimed at identifying the factors contributing to the comorbidity between ADHD and obesity, including genetic factors, fetal programming, executive dysfunctions, psychosocial stress, factors directly related to energy balance, and sleep patterns alterations. The bulk of current research has focused on reduced physical activity and abnormal eating patterns as possible causes of weight gain in individuals with ADHD. Further research is needed to explore the specific role of executive dysfunctions. None of the available published studies have evaluated physiological mechanisms such as hormonal and metabolic disorders or inappropriate neurobiological regulation of appetite. Research exploring the genetic basis for the coexistence of ADHD and obesity and epigenetic mechanisms, with particular emphasis on stress, both pre- and postnatal, seems particularly promising. Here, we propose a biopsychosocial model to integrate current findings and move the field forward to gain insight into the ADHD-obesity relationship.

The findings of neuroimaging studies in children/adolescents with ADHD, and even those of previous meta-analyses, are divergent. Here, Activation Likelihood Estimation meta-analysis, following the current best-practice guidelines, was conducted. We searched multiple databases and traced the references up to June 2018. Then, we extracted the reported coordinates reflecting group comparison between ADHD and healthy subjects from 96 eligible studies, containing 1914 unique participants. The analysis of pooled structural and functional, sub-analyses restricted to modality, and in-/decreased contrast did not yield any significant findings. However, further sub-analyses in the task-fMRI experiments (neutral stimuli only) led to aberrant activity in the left pallidum/putamen and decreased activity (male subjects only) in the left inferior frontal gyrus. The overall findings indicate a lack of regional convergence in children/adolescents with ADHD, which might be due to heterogeneous clinical populations, various experimental design, preprocessing, statistical procedures in individual publications. Our results highlight the need for further high-powered investigations, but may also indicate ADHD pathophysiology might rest in network interactions rather than just regional abnormality.