January 30, 2022
An international team of researchers conducted a comprehensive search of the peer-reviewed literature to perform a meta-analysis, with three aims:
1) assess the global prevalence of adult ADHD
2) explore possible associated factors
3) estimate the 2020 global population of persons with adult ADHD.
In doing so, they distinguished between studies requiring childhood-onset of ADHD to validate adult ADHD (persistent adult ADHD) and studies that make no such requirement and examine ADHD symptoms in adults regardless of previous childhood diagnosis (symptomatic adult ADHD).
The search yielded forty articles covering thirty countries. Twenty reported prevalence data on symptomatic adult ADHD, 19 on persistent adult ADHD, and one on both. Thirty-five studies were published in the last decade (2010-2019). Thirty-one included both urban and rural populations. Thirty-five had a quality score of six or above (out of ten). Twenty-five had sample sizes greater than a thousand.
Because the prevalence of ADHD is age-dependent, and different countries vary widely in the age structure of their populations, the authors adjusted country results for their structures. This allowed for meaningful global estimates of the prevalence of adult ADHD.
Twenty studies covering a total of 107,282 participants reported the prevalence of persistent adult ADHD. The pooled prevalence was 4.6%. After adjustment for the global population structure, the pooled prevalence was 2.6%, equivalent to roughly 140 million cases globally.
Twenty-one studies covering 50,098 participants reported on the prevalence of symptomatic adult ADHD. The pooled prevalence was 8.8%. After adjustment for the global population structure, the pooled prevalence was 6.7%, equivalent to roughly 366 million cases globally.
For persistent adult ADHD, adjusted prevalence declined steeply from 5% among 18- to 24-year-olds to 0.8% among those 60 and older.
For symptomatic adult ADHD, adjusted prevalence declined less steeply from 9% among 18- to 24-year-olds to 4.5% among that 60 and older.
In each case, subgroup analyses found no significant differences based on sex, urban or rural setting, diagnostic tool, DSM version, or investigation period, although pooled prevalence estimates of persistent adult ADHD from 2010 onward were almost twice the previous pooled prevalence estimates. For symptomatic adult ADHD, however, differences between WHO (World Health Organization) regions were highly significant, although the outliers(Southeast Asia at 25% and Eastern Mediterranean at 16%) were based on small samples(304 and 748 respectively).
In both cases, between-study heterogeneity was very high (over 97%). The authors noted, "the age of interviewed participants in the included studies was not unified, ranging from young adults to the elderly. Given the fact that the prevalence of adult ADHD decreases with advancing age, as revealed in previous investigations and our meta-regression, it is not surprising to observe such a diversity in the reported prevalence, and the considerable heterogeneity across included studies could not be fully ruled out by a priori selected variables, including diagnostic tool, DSM version, sex, setting, investigation period, WHO region, and WB [World Bank] region. The effects of other potential correlates of adult ADHD, such as ethnicity, were not able to be addressed due to the lack of sufficient information."
In both cases, there was also evidence of publication bias. The authors stated, "we did not try to eliminate publication bias in our analyses, because we deemed that an observed prevalence of adult ADHD that substantially differed from previous estimates was likely to have been published."
Peige Song, MingmingZha, Qingwen Yang, Yan Zhang, Xue Li,Igor Rudan;on behalf of the Global Health Epidemiology Reference Group (GHERG),"The prevalence of adult attention- deficit hyperactivity disorder: A globalsystematic review and meta-analysis," Journal of Global Health(2021)11:04009,https://doi.org/10.7189/jogh.11.04009.
Organic farming aims to protect biodiversity, promote animal welfare, and avoid using pesticides and fertilizers made from petrochemicals. Some pesticides are designed to target insects’ nervous systems but can also affect brain development and health in larger animals, including humans.
Many people believe organic food is healthier than conventionally produced food, which might be true for certain foods and health factors. But does eating organic food during pregnancy impact the chances of a child developing ADHD or autism spectrum disorder (ASD)?
In Norway, researchers can use detailed national health records to study these connections on a population-wide level, thanks to the country’s single-payer healthcare system and national registries.
The Norwegian Mother, Father, and Child Cohort Study (MoBa) invites parents to participate voluntarily and has a 41% participation rate. The study includes:
For this research, a team tracked 40,707 mother-child pairs from children born between 2002 and 2009. They used questionnaires to measure how much organic food mothers consumed during pregnancy. ADHD and ASD symptoms in children were assessed using validated rating scales.
The final analysis included:
The researchers adjusted for factors like maternal age, education, previous pregnancies, BMI before pregnancy, smoking and alcohol use during pregnancy, birth year and season, and the child’s sex.
The researchers concluded that eating organic food during pregnancy has no meaningful effect on the likelihood of a child developing ADHD or ASD. They stated, “The results do not indicate any clinically significant protective or harmful effects of eating organic food during pregnancy on symptoms of ADHD and ASD in the offspring. Based on these findings, we do not recommend any specific advice regarding intake of organic food during pregnancy.”
Infertility affects about one in six couples worldwide. To address this, medical experts have developed Assisted Reproductive Technologies (ART), including In Vitro Fertilization (IVF) with or without Intra-Cytoplasmic Sperm Injection (ICSI).
Some research suggests that children conceived through ART might have higher rates of intellectual disabilities, cerebral palsy, cancer, and neurological issues compared to children conceived naturally. However, studies looking at a possible link between ART and ADHD have produced mixed and conflicting results.
Until now, there hasn’t been a meta-analysis examining the connection between ART and ADHD. A South Korean research team has conducted the first systematic review and meta-analysis on this topic. Their final analysis included eight studies with a total of over ten million participants, comprising six cohort studies and two cross-sectional studies.
The research focused on two types of studies:
Both types of studies are observational, meaning they don’t involve controlled experiments and can be influenced by confounding factors. So they can document interesting associations, not causality. The studie were mostly large-scale national studies and used clinical ADHD diagnoses.
The researchers concluded that while there may be a small association between ART and ADHD, the effect is minimal, and the results are influenced by differences in study designs. They advised interpreting these findings with caution, noting, “The limited effect size and inherent heterogeneity underscore the need for cautious interpretation.”
Periodontitis, commonly known as gum disease, is a condition where the gums become inflamed. If untreated, it can cause the gums to pull back from the teeth, exposing their base, which may eventually lead to loose teeth or tooth loss. While this condition mostly affects adults, it’s also common among teens who don’t floss or brush their teeth properly.
Until now, only a few small studies have looked at a possible link between ADHD and gum disease. A team in Taiwan recently conducted a nationwide study to explore this connection.
Taiwan has a universal health insurance program, introduced in 1995, that provides medical care to nearly all (99.7%) residents. The Taiwan National Health Research Database collects and oversees all insurance claims, making it an excellent resource for large-scale studies.
The researchers used the database to identify teens aged 12 to 19 with ADHD (diagnosed by a psychiatrist) who had no history of gum disease between 2001 and 2011. These teens made up the ADHD group. They matched each ADHD participant with four teens who didn’t have ADHD or gum disease, creating a control group. The groups were matched by age, gender, enrollment date, family income, place of residence, and other health conditions (like obesity, diabetes, smoking, depression, and substance use).
All diagnoses of gum disease were confirmed by board-certified dentists.
The study included:
The researchers concluded that teens with ADHD have a higher risk of developing gum disease later on, even after accounting for other risk factors like smoking, diabetes, and depression. They stated, “ADHD is an independent risk factor for developing periodontitis.”
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