Attention Deficit Hyperactivity Disorder Symptoms and Psychosis in 22q11.2 Deletion Syndrome

Update on genetics of attention deficit/hyperactivity disorder: current status 2023

PURPOSE OF REVIEW

Attention deficit/hyperactivity disorder (ADHD) shows consistently high heritability in genetic research. In this review article, we give an overview of the analysis of common and rare variants and some insight into current genetic methodology and their link to clinical practice.

RECENT FINDINGS

The heritability of about 80% is also high in comparison to other psychiatric diseases. However, recent studies estimate the proportion of heritability based on single nucleotide variants at 22%. The hidden heritability is an ongoing question in ADHD genetics. Common variants derived from mega genome-wide association analyses (GWAS) and subsequent meta-analyses usually display small effect sizes and explain only a small fraction of phenotypic variance. Rare variants, on the contrary, not only display large effect sizes but also rather explain, due to their rareness, a small fraction on phenotypic variance. Applying polygenic risk score (PRS) analysis is an improved approach of combining effect sizes of many common variants with clinically relevant measures in ADHD.

SUMMARY

We provide a concise overview on how genetic analysis, with a focus on GWAS and PRS, can help explain different behavioural phenotypes in ADHD and how they can be used for diagnosis and therapy prediction. Increased sample sizes of GWAS, meta-analyses and use of PRS is increasingly informative and sets the course for a new era in genetics of ADHD.

Stimulant treatment effectiveness, safety and risk for psychosis in individuals with 22q11.2 deletion syndrome

This study aimed to retrospectively evaluate an association between stimulant treatment for attention-deficit/hyperactivity disorder (ADHD) in individuals with 22q11.2DS and the development of psychotic disorders, to evaluate long-term effectiveness and safety of stimulant treatment in individuals with 22q11.2DS compared to individuals with idiopathic ADHD, and to explore effects of catechol-O-methyltransferase (COMT) genotype on 22q11.2DS response to stimulants and risk of side effects. Rates of stimulant use and methylphenidate equivalent exposure were compared among individuals with 22q11.2DS, between 51 with psychotic disorders and a control group of 57 22q11.2DS without psychotic disorders, from Tel Aviv and Geneva. In addition, 44 individuals with 22q11.2DS and ADHD from Tel Aviv who initiated stimulants before age 18 years were compared to a control group of 35 age- and sex-matched controls with idiopathic ADHD, for treatment effectiveness (Clinical Global Impression Scale-Improvement), and rates of side effects. Stimulant use history and methylphenidate equivalent exposure did not differ among individuals with 22q11.2DS, between those with and without psychotic disorders. The long-term retrospective follow-up (5.3 ± 4.1 years) of stimulant-treated individuals with 22q11.2DS showed a higher rate of significant clinical improvement of ADHD symptoms, compared to idiopathic ADHD individuals (p = 0.013), and similar side effect rates. There was no effect of the COMT genotype on response to stimulants or on any side effects. This preliminary long-term retrospective analysis suggests that stimulant treatment in 22q11.2DS is apparently safe in terms of psychosis conversion and rates of side effects, and that it is effective in alleviating ADHD symptoms.

Relationship between intelligence quotient measures and computerized neurocognitive performance in 22q11.2 deletion syndrome

Intelligence quotient (IQ) testing is standard for evaluating cognitive abilities in genomic studies but requires professional expertise in administration and interpretation, and IQ scores do not translate into insights on implicated brain systems that can link genes to behavior. Individuals with 22q11.2 deletion syndrome (22q11.2DS) often undergo IQ testing to address special needs, but access to testing in resource-limited settings is challenging. The brief Penn Computerized Neurocognitive Battery (CNB) provides measures of cognitive abilities related to brain systems and can screen for cognitive dysfunction. To examine the relation between CNB measures and IQ, we evaluated participants with the 22q11.2DS from Philadelphia and Tel Aviv (N = 117; 52 females; mean age 18.8) who performed both an IQ test and the CNB with a maximum of 5 years between administrations and a subsample (n = 24) who had both IQ and CNB assessments at two time points. We estimated domain-level CNB scores using exploratory factor analysis (including bifactor for overall scores) and related those scores (intraclass correlations (ICCs)) to the IQ scores. We found that the overall CNB accuracy score showed similar correlations between time 1 and time 2 as IQ (0.775 for IQ and 0.721 for CNB accuracy), correlated well with the IQ scores (ICC = 0.565 and 0.593 for time 1 and time 2, respectively), and correlated similarly with adaptive functioning (0.165 and 0.172 for IQ and CNB, respectively). We provide a crosswalk (from linear equating) between standardized CNB and IQ scores. Results suggest that one can substitute the CNB for IQ testing in future genetic studies that aim to probe specific domains of brain-behavior relations beyond IQ.

Pathways to understanding psychosis through rare - 22q11.2DS - and common variants

The 22q11.2 Deletion Syndrome has significant impact on brain and behavior, with about 25% of individuals developing schizophrenia. The condition offers a model for prospective studies on the emergence of psychosis and advancing mechanistic hypotheses on gene-environment interactions, with magnified power for examining genome-phenome association. Here, we highlight findings that build on the International 22q11.2 Brain and Behavior Consortium and relate to several key domains in the study of psychosis-risk and schizophrenia. We examine neurocognition, olfaction and neuroimaging data that indicate similar impairment patterns in this rare syndrome and idiopathic presentation of schizophrenia. We conclude that the converging paradigms, studying psychosis dimensionally in rare and common variants samples, provide complementary approaches that will propel precision medicine in psychiatry.

Effectiveness and side effects of psychopharmacotherapy in individuals with 22q11.2 deletion syndrome with comorbid psychiatric disorders: a systematic review

22q11.2 deletion syndrome (22q11.2DS) is the most common microdeletion in humans and is associated with high rates of attention deficit/hyperactivity disorder (ADHD), psychotic spectrum disorders and mood and anxiety disorders. The objective of the study was to systematically review studies regarding pharmacological treatments for psychiatric disorders in individuals with 22q11.2DS and to provide practical guidelines for the psychiatric management and side effect monitoring in 22q11.2DS. A literature search was conducted using the databases PubMed, PsycINFO and Embase. Information regarding study population, drug treatment, side effect profile and efficacy for each trial was extracted. Data collection was completed on May 2018. The search identified 705 studies. A total of seven studies, describing 182 individuals, were included. Pharmacological interventions included three studies for antipsychotic treatment, two studies for stimulants, one study for selective serotonin reuptake inhibitors (SSRIs), one study for S-adenosyl-L-methionine (SAMe), and one case series for metyrosine. The presented data support the clinical impression that individuals with 22q11.2DS and comorbid psychiatric disorders are treated in a manner comparable to non-22q11.2DS individuals. However, distinct medical comorbidities common in individuals with 22q11.2DS may complicate the administration of pharmacotherapy. Further trials with RCT design, larger sample sizes and more syndrome-specific pharmacological agents are needed to improve evidence-based psychiatric care of 22q11.2DS individuals with comorbid mental disorders.

Sleep problems and associations with psychopathology and cognition in young people with 22q11.2 deletion syndrome (22q11.2DS)

BACKGROUND

Young people with 22q11.2 deletion syndrome (22q11.2DS) are at high risk for neurodevelopmental disorders. Sleep problems may play a role in this risk but their prevalence, nature and links to psychopathology and cognitive function remain undescribed in this population.

METHOD

Sleep problems, psychopathology, developmental coordination and cognitive function were assessed in 140 young people with 22q11.2DS (mean age = 10.1, s.d. = 2.46) and 65 unaffected sibling controls (mean age = 10.8, s.d.SD = 2.26). Primary carers completed questionnaires screening for the children's developmental coordination and autism spectrum disorder.

RESULTS

Sleep problems were identified in 60% of young people with 22q11.2DS compared to 23% of sibling controls (OR 5.00, p < 0.001). Two patterns best-described sleep problems in 22q11.2DS: restless sleep and insomnia. Restless sleep was linked to increased ADHD symptoms (OR 1.16, p < 0.001) and impaired executive function (OR 0.975, p = 0.013). Both patterns were associated with elevated symptoms of anxiety disorder (restless sleep: OR 1.10, p = 0.006 and insomnia: OR 1.07, p = 0.045) and developmental coordination disorder (OR 0.968, p = 0.0023, and OR 0.955, p = 0.009). The insomnia pattern was also linked to elevated conduct disorder symptoms (OR 1.53, p = 0.020).

CONCLUSIONS

Clinicians and carers should be aware that sleep problems are common in 22q11.2DS and index psychiatric risk, cognitive deficits and motor coordination problems. Future studies should explore the physiology of sleep and the links with the neurodevelopment in these young people.

Schizophrenia research in the era of Team Science and big data

The last decade has provided new insights into the genetic architecture of schizophrenia. For the first time researchers have identified genetic factors conferring risk that can be mapped to tissue and cell specific perturbations of the molecular machinery underlying disease processes. However, it has also become clear that attempts to gain mechanistic insights into disease processes that span multiple levels of biological complexity, from genes to cells to circuits to behaviors, are inherently difficult and will require interdisciplinary efforts. Here we discuss the opportunities and pitfalls of developing causal models of SCZ that will lead to novel treatments and prevention strategies. We make the case that integrated large-scale Team Science efforts will be necessary to achieve this goal and that a systems level approach that includes genetics and integrative modelling is needed.

Cognitive deficits in childhood, adolescence and adulthood in 22q11.2 deletion syndrome and association with psychopathology

22q11.2 Deletion Syndrome (22q11.2DS) is associated with high risk of psychiatric disorders and cognitive impairment. It remains unclear to what extent key cognitive skills are associated with psychopathology, and whether cognition is stable over time in 22q11.2DS. 236 children, adolescents and adults with 22q11.2DS and 106 typically developing controls were recruited from three sites across Europe. Measures of IQ, processing speed, sustained attention, spatial working memory and psychiatric assessments were completed. Cognitive performance in individuals was calculated relative to controls in different age groups (children (6-9 years), adolescents (10-17 years), adults (18+ years)). Individuals with 22q11.2DS exhibited cognitive impairment and higher rates of psychiatric disorders compared to typically developing controls. Presence of Autism Spectrum Disorder symptoms was associated with greater deficits in processing speed, sustained attention and working memory in adolescents but not children. Attention deficit hyperactivity disorder in children and adolescents and psychotic disorder in adulthood was associated with sustained attention impairment. Processing speed and working memory were more impaired in children and adults with 22q11.2DS respectively, whereas the deficit in sustained attention was present from childhood and remained static over developmental stages. Psychopathology was associated with cognitive profile of individuals with 22q11.2DS in an age-specific and domain-specific manner. Furthermore, magnitude of cognitive impairment differed by developmental stage in 22q11.2DS and the pattern differed by domain.

Recent developments in understanding the relationship between 22q11.2 deletion syndrome and psychosis

PURPOSE OF REVIEW

Individuals with 22q11.2 deletion syndrome have high rates of comorbid mental illness, particularly psychosis and schizophrenia. The purpose of this review is to summarize recent research in the area of 22q11.2 deletion syndrome and psychosis.

RECENT FINDINGS

Research over the past year has identified negative symptoms, functional impairment, dysphoric mood and a childhood diagnosis of attention deficit hyperactivity disorder as important clinical predictors of psychosis risk in 22q11.2 deletion syndrome. As previously reported in nondeleted schizophrenia, recent studies have implicated neuroinflammation as a possible neurobiological mechanism for psychosis in 22q11.2 deletion syndrome. Recent neuroimaging findings suggest that the cortex is significantly thinner in those with 22q11.2 deletion syndrome and psychosis compared to those without psychosis, replicating similar findings in nondeleted schizophrenia. Further data from the International 22q11.2 Deletion Syndrome Brain and Behavior Consortium have suggested that chromosomal microdeletions are significantly more likely to involve protein-coding genes and several rare copy number variants are associated with the presence of psychosis in deleted individuals.

SUMMARY

There have been several significant recent advances to further characterize the high rates of psychosis in 22q11.2 deletion syndrome, to identify additional clinical predictors of psychosis and to increase our understanding of the neural substrate and genetic aetiology of psychosis in 22q11.2 deletion syndrome.

Attention deficit hyperactivity disorder symptoms as antecedents of later psychotic outcomes in 22q11.2 deletion syndrome

Individuals with 22q11.2 Deletion Syndrome (22q11.2DS) are at substantially heightened risk for psychosis. Thus, prevention and early intervention strategies that target the antecedents of psychosis in this high-risk group are a clinical priority. Attention Deficit Hyperactivity Disorder (ADHD) is one the most prevalent psychiatric disorders in children with 22q11.2DS, particularly the inattentive subtype. The aim of this study was to test the hypothesis that ADHD inattention symptoms predict later psychotic symptoms and/or psychotic disorder in those with 22q11.2DS. 250 children and adolescents with 22q11.2DS without psychotic symptoms at baseline took part in a longitudinal study. Assessments were performed using well-validated structured diagnostic instruments at two time points (T1 (mean age = 11.2, SD = 3.1) and T2 (mean age = 14.3, SD = 3.6)). Inattention symptoms at T1 were associated with development of psychotic symptoms at T2 (OR:1.2, p = 0.01) but weak associations were found with development of psychotic disorder (OR:1.2, p = 0.15). ADHD diagnosis at T1 was strongly associated with development of psychotic symptoms at T2 (OR:4.5, p < 0.001) and psychotic disorder (OR:5.9, p = 0.02). Our findings that inattention symptoms and the diagnosis of ADHD are associated with subsequent psychotic outcomes in 22q11.2DS have important clinical implications. Future studies examining the effects of stimulant and other ADHD treatments on individuals with 22q11.2DS are warranted.

Psychiatric disorders and autism in young children with 22q11.2 deletion syndrome compared to children with idiopathic autism

BACKGROUND

The 22q11.2 deletion syndrome (22q11DS) is a neurogenetic condition characterized by high rates of psychiatric disorders. To our knowledge, this is the first study to assess psychiatric disorders in young children with 22q11DS using a structured psychiatric diagnostic interview, and one of few studies to use the complete gold standard diagnostic evaluation to examine the prevalence of autism spectrum disorder (ASD) in young children with 22q11DS and compare it to a matched control group with iASD.

METHODS

We identified the psychiatric disorders and autistic phenotype of young children with 22q11DS (age 3-8 years) and compared them with those of age and sex-matched children with idiopathic autism (iASD). We used the gold standard psychiatric and ASD assessments including the Autism Diagnostic Interview-Revised (ADI-R), the Autism Diagnostic Observation Schedule (ADOS) and a clinical examination by a child psychiatrist.

RESULTS

Eighty-four percent of the children with 22q11DS had at least one psychiatric disorder, including anxiety disorders and ADHD, and 16% met strict criteria for ASD. Children with 22q11DS and ASD symptoms had less severe overall ASD symptoms than those with iASD. Children with 22q11DS, regardless of ASD diagnosis, were characterized by repetitive restricted behaviors.

CONCLUSIONS

Our results highlight the need to screen for psychiatric disorders in 22q11DS and treat them already in preschool years.

Continuous performance test impairment in a 22q11.2 microdeletion mouse model: improvement by amphetamine

The 22q11.2 deletion syndrome (22q11.2DS) confers high risk of neurodevelopmental disorders such as schizophrenia and attention-deficit hyperactivity disorder. These disorders are associated with attentional impairment, the remediation of which is important for successful therapeutic intervention. We assessed a 22q11.2DS mouse model (Df(h22q11)/+) on a touchscreen rodent continuous performance test (rCPT) of attention and executive function that is analogous to human CPT procedures. Relative to wild-type littermates, Df(h22q11)/+ male mice showed impaired attentional performance as shown by decreased correct response ratio (hit rate) and a reduced ability to discriminate target stimuli from non-target stimuli (discrimination sensitivity, or d'). The Df(h22q11)/+ model exhibited decreased prefrontal cortical-hippocampal oscillatory synchrony within multiple frequency ranges during quiet wakefulness, which may represent a biomarker of cognitive dysfunction. The stimulant amphetamine (0-1.0 mg/kg, i.p.) dose-dependently improved d' in Df(h22q11)/+ mice whereas the highest dose of modafinil (40 mg/kg, i.p.) exacerbated their d' impairment. This is the first report to directly implicate attentional impairment in a 22q11.2DS mouse model, mirroring a key endophenotype of the human disorder. The capacity of the rCPT to detect performance impairments in the 22q11.2DS mouse model, and improvement following psychostimulant-treatment, highlights the utility and translational potential of the Df(h22q11)/+ model and this automated behavioral procedure.

Dependency of prepulse inhibition deficits on baseline startle reactivity in a mouse model of the human 22q11.2 microdeletion syndrome

Hemizygous microdeletion at the chromosomal locus 22q11.2 is a copy number variation with strong genetic linkage to schizophrenia and related disorders. This association, along with its phenotypic overlap with the 22q11.2 microdeletion syndrome, has motivated the establishment of Df[h22q11]/+ mice, in which the human 22q11.2 orthologous region is deleted. Previous investigations using this model showed the presence of reduced prepulse inhibition (PPI) of the acoustic startle reflex, a form of sensorimotor gating known to be impaired in a number of psychiatric disorders. Concomitantly to reduced PPI, however, Df[h22q11]/+ mice are also characterized by a robust increase in baseline startle reactivity, which may complicate or confound the interpretation of PPI. Therefore, the present study re-examined the relationship between acoustic startle reactivity and PPI in this mouse model. We found that while PPI is reduced in Df[h22q11]/+ mice when using its relative indexation (ie, % PPI), this deficit is no longer apparent when using the absolute quantification, that is, the direct comparison between pulse-alone and prepulse-plus-pulse conditions with successively increasing prepulse intensities. We further identified marked negative correlations between % PPI and startle reactivity in Df[h22q11]/+ mice. Moreover, when stratifying Df[h22q11]/+ mice into subgroups displaying low- and high-startle reactivity, only the latter subgroup displayed a significant reduction in % PPI. Collectively, our data suggest that alterations in baseline startle reactivity can confound the outcomes and interpretation of PPI in this mouse model of the human 22q11.2 microdeletion syndrome.