Genetic Nurture and ADHD

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Thirty years ago researchers were looking for "candidate genes" that contributed to ADHD - mutations in genes coding for dopamine receptors or transporter molecules or other parts of the neurochemical systems that had been clearly implicated in ADHD. And they found them! But it turned out that these genes appear to contribute to the development of ADHD only in some families, and not in general. Since then the search for genetic contributions to ADHD has broadened. In addition to strong effects from candidate genes, the inheritance of ADHD is affects by: polygenic effects (hundreds of genes, each of which have tiny effects, and many of which increase the risk for having any mental health condition), mitochondrial genes (which are inherited separately from nuclear genes), copy number variants (where sections of thousands of base pairs of DNA are either duplicated or deleted), and epigenetic effects (how DNA is modified to turn on or off specific genes).

A recent study of a million Swedish kids has documented an additional genetic factor. Using knowledge of who developed ADHD, and which relatives (siblings, half siblings, and cousins) did as well, they calculated the genetic maternal nurturance effect - which is the extent to which the mother's genetics shape the environment she creates for her offspring which influences their development of ADHD. This is distinct from the direct effect of passing on, on average, 50% of her genes. The direct genetic effects contributed 66% of the likelihood of developing ADHD, while the genetic maternal nurturance effect was smaller - 14%, but not negligible. Genetic paternal nurturance effects appear to be considerably smaller. The study did not directly explore which aspects of the nurturing environment were influenced by mother's genes, but previous work indicate that exposure to cigarette smoke, stress/PTSD, and poverty may all be involved.

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References:

Significant Role for Maternal Genetic Nurture in the Risk Architecture of Attention Deficit Hyperactivity Disorder (2025)

Copy Number Variant Architecture of Child Psychopathology and Cognitive Development in the ABCD Study (2025)

Mitochondrial DNA haplogroups and risk of attention deficit and hyperactivity disorder in European Americans (2020)

Population and familial association between the D4 dopamine receptor gene and measures of Novelty Seeking (1996)

Full Chapter list:

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Psychiatrist, neuroscientist, and author John Kruse, MD, PhD presents practical, actionable, well-researched information about treatment options that scientists and clinicians recommend for adult ADHD and other mental health conditions.

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