January 14, 2022
Inhibitory control is an essential cognitive control function whereby the prefrontal cortex blocks planned motor actions or interrupts motor actions already initiated by other parts of the brain. For example, someone might instinctually reach for a candy bar but then put it back upon thinking that eating it would conflict with a higher-level goal of cutting down on sugar consumption. Impairment of inhibitory control is a known characteristic of several psychiatric disorders, including ADHD.
Any generally safe treatment with the ability to at least partially reverse such impairment would therefore be useful. Researchers are currently experimenting with transcranial direct current stimulation, a non-invasive brain stimulation technique that uses a weak electrical current to stimulate specific regions of the brain.
What, then, do we know so far about its potential effectiveness for improving inhibitory control?
A team of experts at the University of Tübingen in Germany conducted a comprehensive search of the peer-reviewed medical literature to find out. They then performed a meta-analysis of 45 studies with a combined total of over 1,600 participants. All but four of the studies used sham or other active controls.
The overall meta-analysis found a significant but small improvement in response inhibition. But it also found evidence of publication bias. Adjusting for publication bias reduced the effect size in half, to a tiny but still significant improvement.
The meta-analysis relied on two behavioral tasks that require inhibitory control to measure response inhibition: the go-/no-task, and the stop-signal task. Separating these, there was no significant improvement in the go/no-go task performance. All the improvement was concentrated on the stop-signal task.
The authors noted, "A potential limitation of this meta-analysis is that we could not exhaustively model-dependent relationships between moderator variables (e.g., tDCS polarity and electrode placement)," and "Further high-quality studies are needed to investigate potential interactions between technical and functional parameters in tDCS research."
Philipp A.Schroeder, Tobias Schwippel, Ines Wolz, Jennifer Svaldi, "Meta-Analysis Of The Effects Of Transcranial Direct Current Stimulation On Inhibitory Control," BrainStimulation(2020),https://doi.org/10.1016/j.brs.2020.05.006.
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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