The influence of genes on the development of symptoms of attention deficit hyperactivity disorder

Autistic spectrum disorder ASD: Learning disabilities can include developmental speech and language disorders and academic skills disorders. Adolescents and adults with ADHD are at increased risk of substance abuse. They can also occur as a side effect of medications used to treat ADHD.

The influence of genes on the development of symptoms of attention deficit hyperactivity disorder

Published online Nov To view a copy of this license, visit http: Results of candidate gene as well as genome-wide molecular genetic studies in aADHD samples implicate some of the same genes involved in ADHD in children, although in some cases different alleles and different genes may be responsible for adult versus childhood ADHD.

In addition, studies of rare genetic variants have identified probable causative mutations for aADHD. Use of endophenotypes based on neuropsychology and neuroimaging, as well as next-generation genome analysis and improved statistical and bioinformatic analysis methods hold the promise of identifying additional genetic variants involved in disease etiology.

Large, international collaborations have paved the way for well-powered studies. Progress in identifying aADHD risk genes may provide us with tools for the prediction of disease progression in the clinic and better treatment, and ultimately may help to prevent persistence of ADHD into adulthood.

Symptoms of inattention, impulsiveness, restlessness and emotional dysregulation in adults were considered not to reflect ADHD, but to be unspecific problems secondary to other disorders.

This idea was challenged when systematic follow-up studies of children documented the persistence of ADHD into adulthood. The notion that the total number of people affected by aADHD is even larger than those suffering from ADHD during childhood and adolescence also shows that the societal consequences of this chronic debilitating condition may have been vastly underestimated in the past.

The lack of age-appropriate clinical measures has hampered progress in this field, including genetic research. Future versions of the Diagnostic and Statistical Manual of Mental Disorders 1 may provide diagnostic measures that are better suited for all relevant age groups.

Longitudinal twin studies show that the continuity of symptoms from childhood through to adolescence is predominantly due to common genetic influences. Genetic research on ADHD started with the finding that hyperactivity tends to aggregate in families.

Adoption studies found that ADHD is transmitted only to biological relatives, which strongly implicates genetic factors as the main causal influences on familial risk for the disorder. However, both adoption and family studies identify discrepancies related to different sources of ratings, with self-evaluation of ADHD symptoms by adults providing less evidence of familial effects than informants or cognitive performance data.

The situation is similar in adolescence, as adolescent twin studies using self-ratings show lower heritability estimates than studies of parent or teacher ratings, 2627 suggesting that self-ratings may be a poorer measure of the underlying genetic liability to ADHD than informant reports or clinical interviews.

Although the estimated heritability in self-rated ADHD symptoms in adult populations is lower than that derived from parent or teacher ratings of cADHD, the pattern of findings is identical. This suggests that for both child and adult ADHD the disorder is best perceived as the impairing extreme of a quantitative trait Larsson et al.


Despite these common features, the relatively low heritability estimates for ADHD symptoms in adults derived from population twin studies need some explanation, because they appear to be at odds with heritability estimates of ADHD symptoms in children, as well as the family studies that show a high familial risk for persistent forms of ADHD.

We have already mentioned the consistent finding that self-ratings of ADHD symptoms give lower estimates of heritability compared with informant ratings in twin studies. One source of measurement error that is, variance of the true diagnostic status that is not predicted by the measurement instrument is the reliability of the self-rated measures of ADHD symptoms.

In one of the heritability studies by Boomsma and co-workers, 25 this was estimated to be around 0. For example, Kessler et al. Similar findings were reported by Daigre Blanco et al. Single raters may inflate identical twin pair similarities, potentially leading to an overestimation of heritability in the reported studies on cADHD, whereas the lower reliability of ratings between two raters may lead to lower estimates.

Another relevant difference between child and adult samples is the expected range of ADHD symptom scores. It is well known that ADHD symptoms decline through adolescence into adulthood.

Although some of this symptom decline is likely due to true remission of ADHD, some have argued that the diagnostic criteria for ADHD, which were originally developed for children, are developmentally insensitive and thus become less sensitive to ADHD with age see above and refs.

Added to this is the possibility that in cross-sectional studies of adult population twin studies that do not apply clinical criteria for ADHDADHD symptoms may emerge in some individuals owing to adult-onset conditions, such as anxiety, depression and drug use.

The influence of genes on the development of symptoms of attention deficit hyperactivity disorder

The family studies that showed high familial risk for ADHD used case—control methods to ascertain adult patients who were self-referred for severe ADHD-like problems. There are notable differences between the clinically referred and population-based samples.

The former have a more skewed male-to-female ratio, higher rates of psychiatric comorbidity and lower rates of primarily inattentive ADHD. Moreover, the family and twin studies used differing assessment methodologies. The family studies diagnosed subjects with structured interviews that evaluated childhood onset of impairing symptoms and the presence of impairment in multiple settings as required by Diagnostic and Statistical Manual of Mental Disorders, 4th Edition.

In contrast, with the exception of Schultz et al. Analogous to this, cluster A personality disorders show low heritability estimates in analyses based on limited phenotypic information that become much higher when adding more information from interviews. This might reflect the importance of developmental processes that are sensitive to person-specific environmental factors affecting the longitudinal outcome of ADHD in adults.Attention deficit hyperactivity disorder (ADHD) is a mental disorder of the neurodevelopmental type.

It is characterized by problems paying attention, excessive activity, or diffi. Anywhere from one-third to one-half of parents with ADHD will have a child with the disorder.

There are genetic characteristics that seem to be passed down. Attention (). deficit/hyperactivity disorder across the lifespan. Annual Review of Medicine, Knouse, LE, & Safren, SA (), Current Status of Cognitive Behavioral Therapy for.

Attention-deficit hyperactivity disorder (ADHD) is a mental disorder of the neurodevelopmental type. [9] [10] It is characterized by problems paying attention, excessive activity, or difficulty controlling behavior . However, to our knowledge, no study to date has examined the genetic and environmental influences explaining interindividual differences in the developmental course of ADHD symptoms from childhood to adolescence (ie, systematic decreases or increases with age).

The most accurate statement with regard to the genetic influences of attention deficit/hyperactivity disorder is: there appear to be multiple genetic influences Ron is a 9-year-old boy recently diagnosed with attention deficit/hyperactivity disorder.