Nature and nurture in neuropsychiatric genetics: where do we stand?

Temporal trends and age-period-cohort analysis of depression in U.S. adults from 2013 to 2022

BACKGROUND

In the United States, the lifetime prevalence of depression in the US population is 20.6 %. We aimed to understand the temporal trends in the prevalence of depression among adults in the United States during the period 2013-2022 as well as the effects of age, period, and cohort effects on the prevalence of depression.

METHODS

Data from 3,139,488 participants in the U.S. Behavioral Risk Factor Surveillance System (BRFSS) from 2013 to 2022 were used in this study. The joinpoint regression model was used to calculate annual percentage change (APC) and average annual percentage change (AAPC) to learn about the time trends in the prevalence of depression. Age-period-cohort models were used to estimate the effects of age, period, and birth cohort effects on the prevalence of depression.

RESULTS

The prevalence of depression among adults in the United States showed an overall increasing trend from 2013 to 2022. The rate of increase was greater in males than females, with AAPC values of 1.44 % (95 % CI: 0.32-2.18), and 1.23 % (95 % CI: 0.32-2.25), respectively. Regarding the age effect, the risk of depression among adults in the United States generally showed an increasing and then decreasing trend with age. The risk of developing the condition reached its maximum at 50-54 years (RR = 1.28, 95 % CI = 1.26-1.30). Regarding the period effect, the risk of depression among US adults was higher during 2018-2022 than during 2013-2017. The overall cohort effect for depression prevalence was a higher risk for those born later, with a maximum RR of 1.51 (95 % CI: 1.47-1.54).

CONCLUSION

The prevalence of adult depression in the United States is showing an increasing trend. Middle-aged people and those born later in life deserve more attention as high-risk groups. It is recommended that the condition burden of depression be reduced with the promotion of healthy lifestyles, the promotion of interpersonal communication, as well as enhanced mental health education and mental health literacy.

The Difficult Path to the Discovery of Novel Treatments in Psychiatric Disorders

CNS diseases, including psychiatric disorders, represent a significant opportunity for the discovery and development of new drugs and therapeutic treatments with the potential to have a significant impact on human health. CNS diseases, however, present particular challenges to therapeutic discovery efforts, and psychiatric diseases/disorders may be among the most difficult. With specific exceptions such as psychostimulants for ADHD, a large number of psychiatric patients are resistant to existing treatments. In addition, clinicians have no way of knowing which psychiatric patients will respond to which drugs. By definition, psychiatric diagnoses are syndromal in nature; determinations of efficacy are often self-reported, and drug discovery is largely model-based. While such models of psychiatric disease are amenable to screening for new drugs, whether cellular or whole-animal based, they have only modest face validity and, more importantly, predictive validity. Multiple academic, pharmaceutical industry, and government agencies are dedicated to the translation of new findings about the neurobiology of major psychiatric disorders into the discovery and advancement of novel therapies. The collaboration of these agencies provide a pathway for developing new therapeutics. These efforts will be greatly helped by recent advances in understanding the genetic bases of psychiatric disorders, the ongoing search for diagnostic and therapy-responsive biomarkers, and the validation of new animal models.

Non-genetic factors that influence methamphetamine intake in a genetic model of differential methamphetamine consumption

RATIONALE

Genetic and non-genetic factors influence substance use disorders. Our previous work in genetic mouse models focused on genetic factors that influence methamphetamine (MA) intake. The current research examined several non-genetic factors for their potential influence on this trait.

OBJECTIVES

We examined the impact on MA intake of several non-genetic factors, including MA access schedule, prior forced MA exposure, concomitant ethanol (EtOH) access, and gamma-aminobutyric acid type B (GABAB) receptor activation. Selectively bred MA high drinking (MAHDR) and low drinking (MALDR) mice participated in this research.

RESULTS

MAHDR, but not MALDR, mice increased MA intake when given intermittent access, compared with continuous access, with a water choice under both schedules. MA intake was not altered by previous exposure to forced MA consumption. Male MAHDR mice given simultaneous access to MA, EtOH, and an EtOH+MA mixture exhibited a strong preference for MA over EtOH and EtOH+MA; MA intake was not affected by EtOH in female MAHDR mice. When independent MAHDR groups were given access to MA, EtOH, or EtOH+MA vs. water in each case, MA intake was reduced in the water vs. EtOH+MA group, compared with the water vs. MA group. The GABAB receptor agonist R(+)-baclofen (BAC) not only reduced MA intake but also reduced water intake and locomotor activity in MAHDR mice. There was a residual effect of BAC, such that MA intake was increased after termination of BAC treatment.

CONCLUSIONS

These findings demonstrate that voluntary MA intake in MAHDR mice is influenced by non-genetic factors related to MA access schedule and co-morbid EtOH exposure.

Using the tools of genetic epidemiology to understand sex differences in neuropsychiatric disorders

Many neuropsychiatric disorders exhibit differences in prevalence, age of onset, symptoms or course of illness between males and females. For the most part, the origins of these differences are not well understood. In this article, we provide an overview of sex differences in psychiatric disorders including autism spectrum disorder (ASD), attention deficit/hyperactivity disorder (ADHD), anxiety, depression, alcohol and substance abuse, schizophrenia, eating disorders and risk of suicide. We discuss both genetic and nongenetic mechanisms that have been hypothesized to underlie these differences, including ascertainment bias, environmental stressors, X‐ or Y‐linked risk loci, and differential liability thresholds in males and females. We then review the use of twin, family and genome‐wide association approaches to study potential genetic mechanisms of sex differences and the extent to which these designs have been employed in studies of psychiatric disorders. We describe the utility of genetic epidemiologic study designs, including classical twin and family studies, large‐scale studies of population registries, derived recurrence risks, and molecular genetic analyses of genome‐wide variation that may enhance our understanding sex differences in neuropsychiatric disorders.

FinnTwin12 Cohort: An Updated Review

This review offers an update on research conducted with FinnTwin12 (FT12), the youngest of the three Finnish Twin Cohorts. FT12 was designed as a two-stage study. In the first stage, we conducted multiwave questionnaire research enrolling all eligible twins born in Finland during 1983-1987 along with their biological parents. In stage 2, we intensively studied a subset of these twins with in-school assessments at age 12 and semistructured poly-diagnostic interviews at age 14. At baseline, parents of intensively studied twins were administered the adult version of the interview. Laboratory studies with repeat interviews, neuropsychological tests, and collection of DNA were made of intensively studied twins during follow-up in early adulthood. The basic aim of the FT12 study design was to obtain information on individual, familial and school/neighborhood risks for substance use/abuse prior to the onset of regular tobacco and alcohol use and then track trajectories of use and abuse and their consequences into adulthood. But the longitudinal assessments were not narrowly limited to this basic aim, and with multiwave, multirater assessments from ages 11 to 12, the study has created a richly informative data set for analyses of gene-environment interactions of both candidate genes and genomewide measures with measured risk-relevant environments. Because 25 years have elapsed since the start of the study, we are planning a fifth-wave follow-up assessment.

Drugs of Abuse Induced-Subversion of the Peripheral Immune Response and Central Glial Activity: Focus on Novel Therapeutic Approaches

BACKGROUND

Drugs of abuse affect both central nervous system (CNS) and peripheral immune function. Besides the involvement of dopamine and glutamate systems, chronic exposure to drugs of abuse alters immune homeostasis, promoting a pro-inflammatory status. At the same time, impaired peripheral immunity leads to an increased susceptibility to infections in drug abusers.

DISCUSSION

There is evidence that certain drugs, such as opioids, activate microglial cells and astrocytes which, in turn, provoke central neuroinflammation. Particularly, opioids bind the Toll-like receptor (TLR)-4 with increased expression of nuclear factor kappa-light-chain-enhancer of activated B cells and release of pro-inflammatory cytokines. Peripheral mediators released by immune cells also contribute to aggravate central neuroinflammation.

CONCLUSION

These are based either on the inhibition of TLR-4 activation by drugs of abuse or on the correction of dopamine and glutamate pathways. Finally, a hypothetic nutraceutical intervention with polyphenols in view of their anti-inflammatory and anti-oxidant properties will be outlined as an adjuvant treatment for drugs of abuse-related disorders.

Environmental Exposures and Neuropsychiatric Disorders: What Role Does the Gut-Immune-Brain Axis Play?

PURPOSE OF REVIEW

Evidence is growing that environmental exposures-including xenobiotics as well as microbes-play a role in the pathogenesis of many neuropsychiatric disorders. Underlying mechanisms are likely to be complex, involving the developmentally sensitive interplay of genetic/epigenetic, detoxification, and immune factors. Here, we review evidence supporting a role for environmental factors and disrupted gut-immune-brain axis function in some neuropsychiatric conditions.

RECENT FINDINGS

Studies suggesting the involvement of an altered microbiome in triggering CNS-directed autoimmunity and neuropsychiatric disturbances are presented as an intriguing example of the varied mechanisms by which environmentally induced gut-immune-brain axis dysfunction may contribute to adverse brain outcomes. The gut-immune-brain axis is a burgeoning frontier for investigation of neuropsychiatric illness. Future translational research to define individual responses to exogenous exposures in terms of microbiome-dependent skew of the metabolome, immunity, and brain function may serve as a lens for illumination of pathways involved in the development of CNS disease and fuel discovery of novel interventions.

Paternal and maternal age as risk factors for schizophrenia: a case-control study

OBJECTIVE

Advanced parental age might constitute a generic risk factor for mental and somatic disorders. The current study tested whether this concerns also patients with schizophrenia.

METHODS

A total of 231 schizophrenic, 56 other severe mental disorders patients and 204 controls were diagnosed according to DSM-IV-TR. Data were tested with ANOVA models including relative risk and odds ratios.

RESULTS

Patients with schizophrenia manifested higher paternal (32.55 ± 6.35 vs. 29.42 ± 6.07, p < .001) and maternal age (27.66 ± 5.57 vs. 25.46 ± 4.52, p < .001). Patients with other mental disorders had higher paternal (33.29 ± 8.35; p = .001) but not maternal age (26.69 ± 5.89; p = .296) compared to controls. There was no difference between the two patient groups concerning either paternal or maternal age (p > .05). There seems to be a higher risk for the development of schizophrenia in offspring with paternal age above 25 years and maternal age above 22 years at delivery.

CONCLUSIONS

The current study provides further support for the suggestion that advanced paternal age constitutes a risk factor (in a non-dose dependent and gender-independent way) for the development of schizophrenia but also for other mental disorders. In contrast, advanced maternal age characterises schizophrenia specifically. The higher risk is evident after 25 years of paternal and 22 years of maternal age, respectively.

Shaping vulnerability to addiction - the contribution of behavior, neural circuits and molecular mechanisms

Substance use disorders continue to impose increasing medical, financial and emotional burdens on society in the form of morbidity and overdose, family disintegration, loss of employment and crime, while advances in prevention and treatment options remain limited. Importantly, not all individuals exposed to abused substances effectively develop the disease. Genetic factors play a significant role in determining addiction vulnerability and interactions between innate predisposition, environmental factors and personal experiences are also critical. Thus, understanding individual differences that contribute to the initiation of substance use as well as on long-term maladaptations driving compulsive drug use and relapse propensity is of critical importance to reduce this devastating disorder. In this paper, we discuss current topics in the field of addiction regarding individual vulnerability related to behavioral endophenotypes, neural circuits, as well as genetics and epigenetic mechanisms. Expanded knowledge of these factors is of importance to improve and personalize prevention and treatment interventions in the future.

Behavioral and Brain Activity Indices of Cognitive Control Deficits in Binge Drinkers

Heavy episodic drinking is prevalent among young adults and is a public issue of increasing importance. Its initiation and maintenance are associated with deficits in the capacity to inhibit automatic processing in favor of non-habitual responses. This study used functional magnetic resonance imaging (fMRI) to examine behavioral and brain activity indices of cognitive control during the Stroop task as a function of binge drinking. Heavy episodic drinkers (HED) reported consuming 5+/6+ drinks in two hours at least five times in the past six months and were compared to light drinkers (LED) who reported two or fewer binge episodes but were matched on demographics, intelligence and family history of alcoholism. Greater conflict-induced activity in the ventrolateral prefrontal cortex (VLPFC) and thalamus was observed in HED participants and it was positively correlated with alcohol intake and alcohol-related harmful consequences. HEDs maintained intact accuracy but at a cost of prolonged reaction times to high-conflict trials and increased ratings of task difficulty. Greater activation of the areas implicated in cognitive control is consistent with compensatory network expansion to meet higher cognitive demands. These results provide further insight into degradation of cognitive control in HEDs which may benefit development of detection and prevention strategies.

Stress and the Emerging Roles of Chromatin Remodeling in Signal Integration and Stable Transmission of Reversible Phenotypes

The influence of early life experience and degree of parental-infant attachment on emotional development in children and adolescents has been comprehensively studied. Structural and mechanistic insight into the biological foundation and maintenance of mammalian defensive systems (metabolic, immune, nervous and behavioral) is slowly advancing through the emerging field of developmental molecular (epi)genetics. Initial evidence revealed that differential nurture early in life generates stable differences in offspring hypothalamic-pituitary-adrenal (HPA) regulation, in part, through chromatin remodeling and changes in DNA methylation of specific genes expressed in the brain, revealing physical, biochemical and molecular paths for the epidemiological concept of gene-environment interactions. Herein, a primary molecular mechanism underpinning the early developmental programming and lifelong maintenance of defensive (emotional) responses in the offspring is the alteration of chromatin domains of specific genomic regions from a condensed state (heterochromatin) to a transcriptionally accessible state (euchromatin). Conversely, DNA methylation promotes the formation of heterochromatin, which is essential for gene silencing, genomic integrity and chromosome segregation. Therefore, inter-individual differences in chromatin modifications and DNA methylation marks hold great potential for assessing the impact of both early life experience and effectiveness of intervention programs—from guided psychosocial strategies focused on changing behavior to pharmacological treatments that target chromatin remodeling and DNA methylation enzymes to dietary approaches that alter cellular pools of metabolic intermediates and methyl donors to affect nutrient bioavailability and metabolism. In this review article, we discuss the potential molecular mechanism(s) of gene regulation associated with chromatin modeling and programming of endocrine (e.g., HPA and metabolic or cardiovascular) and behavioral (e.g., fearfulness, vigilance) responses to stress, including alterations in DNA methylation and the role of DNA repair machinery. From parental history (e.g., drugs, housing, illness, nutrition, socialization) to maternal-offspring exchanges of nutrition, microbiota, antibodies and stimulation, the nature of nurture provides not only mechanistic insight into how experiences propagate from external to internal variables, but also identifies a composite therapeutic target, chromatin modeling, for gestational/prenatal stress, adolescent anxiety/depression and adult-onset neuropsychiatric disease.

Genetic influences on adolescent behavior

Adolescence is a transitional, developmental phase with marked shifts in behavior, particularly as related to risk-taking and experimentation. Genetic influences on adolescent behavior also show marked changes across this developmental period; in fact, adolescence showcases the dynamic nature of genetic influences on human behavior. Using the twin studies literature on alcohol use and misuse, we highlight several principles of genetic influence on adolescent behavior. We illustrate how genetic influences change (increase) across adolescence, as individuals have more freedom to express their predispositions and to shape their social worlds. We show how there are multiple genetic pathways to risk, and how the environment can moderate the importance of genetic predispositions. Finally, we review the literature aimed at identifying specific genes involved in adolescent behavior and understanding how identified genes impact adolescent outcomes. Ultimately, understanding how genetic predispositions combine with environmental influences to impact pathways of risk and resilience should be translated into improved prevention and intervention efforts; this remains a rich area for future research.

Smooth pursuit eye movements and schizophrenia: literature review

OBJECTIVE

To review the scientific literature about the relationship between impairment on smooth pursuit eye movements and schizophrenia.

METHODS

Narrative review that includes historical articles, reports about basic and clinical investigation, systematic reviews, and meta-analysis on the topic.

RESULTS

Up to 80% of schizophrenic patients have impairment of smooth pursuit eye movements. Despite the diversity of test protocols, 65% of patients and controls are correctly classified by their overall performance during this pursuit. The smooth pursuit eye movements depend on the ability to anticipate the target's velocity and the visual feedback, as well as on learning and attention. The neuroanatomy implicated in smooth pursuit overlaps to some extent with certain frontal cortex zones associated with some clinical and neuropsychological characteristics of the schizophrenia, therefore some specific components of smooth pursuit anomalies could serve as biomarkers of the disease. Due to their sedative effect, antipsychotics have a deleterious effect on smooth pursuit eye movements, thus these movements cannot be used to evaluate the efficacy of the currently available treatments.

CONCLUSION

Standardized evaluation of smooth pursuit eye movements on schizophrenia will allow to use specific aspects of that pursuit as biomarkers for the study of its genetics, psychopathology, or neuropsychology.

Novel siRNA delivery strategy: a new "strand" in CNS translational medicine?

RNA interference has been envisaged as a powerful tool for molecular and clinical investigation with a great potential for clinical applications. In recent years, increased understanding of cancer biology and stem cell biology has dramatically accelerated the development of technology for cell and gene therapy in these areas. This paper is a review of the most recent report of innovative use of siRNA to benefit several central nervous system diseases. Furthermore, a description is made of innovative strategies of delivery into the brain by means of viral and non-viral vectors with high potential for translation into clinical use. Problems are also highlighted that might hamper the transition from bench to bed, analyzing the lack of reliable preclinical models with predictive validity and the lack of effective delivery systems, which are able to overcome biological barriers and specifically reach the brain site of action.

Integrating early life experience, gene expression, brain development, and emergent phenotypes: unraveling the thread of nature via nurture

Adaptation to environmental changes is based on the perpetual generation of new phenotypes. Modern biology has focused on the role of epigenetic mechanisms in facilitating the adaptation of organisms to changing environments through alterations in gene expression. Inherited and/or acquired epigenetic factors are relatively stable and have regulatory roles in numerous genomic activities that translate into phenotypic outcomes. Evidence that dietary and pharmacological interventions have the potential to reverse environment-induced modification of epigenetic states (e.g., early life experience, nutrition, medication, infection) has provided an additional stimulus for understanding the biological basis of individual differences in cognitive abilities and disorders of the brain. It has been suggested that accurate quantification of the relative contribution of heritable genetic and epigenetic variation is essential for understanding phenotypic divergence and adaptation in changing environments, a process requiring stable modulation of gene expression. The main challenge for epigenetics in psychology and psychiatry is to determine how experiences and environmental cues, including the nature of our nurture, influence the expression of neuronal genes to produce long-term individual differences in behavior, cognition, personality, and mental health. To this end, focusing on DNA and histone modifications and their initiators, mediators and readers may provide new inroads for understanding the molecular basis of phenotypic plasticity and disorders of the brain. In this chapter, we review recent discoveries highlighting epigenetic aspects of normal brain development and mental illness, as well as discuss some future directions in the field of behavioral epigenetics.

Genetics and psychiatry: a proposal for the application of the precautionary principle

The paper suggests an application of the precautionary principle to the use of genetics in psychiatry focusing on scientific uncertainty. Different levels of uncertainty are taken into consideration--from the acknowledgement that the genetic paradigm is only one of the possible ways to explain psychiatric disorders, via the difficulties related to the diagnostic path and genetic methods, to the value of the results of studies carried out in this field. Considering those uncertainties, some measures for the use of genetics in psychiatry are suggested. Some of those measures are related to the conceptual limits of the genetic paradigm; others are related to present knowledge and should be re-evaluated.

Transgenic mouse models for ADHD

Attention-deficit hyperactivity disorder (ADHD) is a developmental disorder characterized by symptoms of inattention, impulsivity and hyperactivity that adversely affect many aspects of life. Whereas the etiology of ADHD remains unknown, growing evidence indicates a genetic involvement in the development of this disorder. The brain circuits associated with ADHD are rich in monoamines, which are involved in the mechanism of action of psychostimulants and other medications used to treat this disorder. Dopamine (DA) is believed to play a major role in ADHD but other neurotransmitters are certainly also involved. Genetically modified mice have become an indispensable tool used to analyze the contribution of genetic factors in the pathogenesis of human disorders. Although rodent models cannot fully recapitulate complex human psychiatric disorders such as ADHD, transgenic mice offer an opportunity to directly investigate in vivo the specific roles of novel candidate genes identified in ADHD patients. Several knock-out and transgenic mouse models have been proposed as ADHD models, mostly based on targeting genes involved in DA transmission, including the gene encoding the dopamine transporter (DAT1). These mutant models provided an opportunity to evaluate the contribution of dopamine-related processes to brain pathology, to dissect the neuronal circuitry and molecular mechanisms involved in the antihyperkinetic action of psychostimulants and to evaluate novel treatments for ADHD. New transgenic models mouse models targeting other genes have recently been proposed for ADHD. Here, we discuss the recent advances and pitfalls in modeling ADHD endophenotypes in genetically altered animals.

Effect of maternal lipopolysaccharide administration on the development of dopaminergic receptors and transporter in the rat offspring

Epidemiological evidence supports that maternal infection during gestation are notable risk factors for developmental mental illnesses including schizophrenia and autism. In prenatal lipopolysaccharide (LPS) model of immune activation in rats, the offspring exhibit significant impairments in behaviors mediated by central dopamine (DA) system. This study aimed to examine the temporal and regional pattern of postnatal DA development in the male offspring of pregnant Sprague-Dawley rats administered with 100 µg/kg LPS or saline at gestational days 15/16. Using ligand autoradiography, D1 and D2 dopamine receptors (D1R, D2R) and dopamine transporter (DAT) binding levels were measured in the prefrontal cortex (PFC) and sub cortical regions (dorsal striatum and nucleus accumbens core and shell) at pre pubertal (P35) and post pubertal ages (P60). We found a significant decrease in D2R ligand [(3)H] YM-90151-2 binding in the medial PFC (mPFC) in prenatal LPS-treated animals at P35 and P60 compared to respective saline groups. The decrease in D2R levels was not observed in the striatum or accumbens of maternal LPS-treated animals. No significant changes were observed in [(3)H] SCH23390 binding to D1R. However, the level of [(125)I] RTI-121 binding to DAT was selectively reduced in the nucleus accumbens core and shell at P35 in the prenatal LPS group. Immunohistochemical analysis showed that number of D2R immunopositive cells in infralimbic/prelimbic (IL/PL) part of mPFC was significantly reduced in the LPS group at P60. Prenatal LPS treatment did not significantly affect either the total number of mature neurons or parvalbumin (PV)-immunopositive interneurons in this region. However the number of PV and D2R co-labeled neurons was significantly reduced in the IL/PL subregion of PFC of LPS treated animals. Our data suggests D2R deficit in the PFC and PV interneurons may be relevant to understanding mechanisms of cortical dysfunctions described in prenatal infection animal models as well as schizophrenia.

Modelling the contribution of family history and variation in single nucleotide polymorphisms to risk of schizophrenia: a Danish national birth cohort-based study

BACKGROUND

Epidemiological studies indicate that having any family member with schizophrenia increases the risk of schizophrenia in the probands. However, genome-wide association studies (GWAS) have accounted for little of this variation. The aim of this study was to use a population-based sample to explore the influence of single-nucleotide polymorphisms (SNPs) on the excess schizophrenia risk in offspring of parents with a psychotic, bipolar affective or other psychiatric disorder.

METHOD

A nested case-control study with 739 cases with schizophrenia and 800 controls. Their parents and siblings. Information from national health registers and GWAS data from the national neonatal biobank.

RESULTS

Offspring schizophrenia risk was elevated in those whose mother, father or siblings had been diagnosed with schizophrenia or related psychosis, bipolar affective disorder or any other psychiatric disorder. The rate ratio was 9.31 (3.85; 22.44) in offspring whose 1st degree relative was diagnosed with schizophrenia. This rate ranged between 8.31 and 11.34 when adjusted for each SNP individually and shrank to 8.23 (3.13; 21.64) when adjusted for 25% of the SNP-variation in candidate genes. The percentage of the excess risk associated with a family history of schizophrenia mediated through genome-wide SNP-variation ranged between -6.1%(-17.0%;2.6%) and 4.1%(-3.9%;15.2%). Analogous results were seen for each parent and for histories of bipolar affective and other psychiatric diagnoses.

CONCLUSIONS

The excess risk of schizophrenia in offspring of parents who have a psychotic, bipolar affective or other psychiatric disorder is not currently explained by the SNP variation included in this study in accordance with findings from published genetic studies.

A new public health genomics model for common complex diseases, with an application to common behavioral disorders

AIM

In the light of common forms of gene-environment interplay, particularly epigenomics and ecogenetics, the incorporation of envirome data into public health genomics models becomes necessary. Developing and restructuring public health genomics models is essential within the context of common complex diseases.

MATERIALS & METHODS

We developed a novel theoretical model integrating a gene-environment interaction paradigm into public health genomics, which integrates four main sources of data: personal genome data, personal envirome data, molecular genetic/genomic evidence and environmental factors implicated in gene-environment interactions underlying common complex disease phenotypes. Collectively, this knowledge is fed into public health policy development.

RESULTS

This model is the first public health genomics model that incorporates gene-environment interactions within the context of common complex disorders, and is applied to behavioral conditions.

CONCLUSION

Our model proposes, for the first time, an understanding of behavioral disorders from the genomic perspective, combining it with known environmental factors within the framework of public health. Application of this model will enable evidence-based behavioral interventions at the public health level and facilitate genome-based public health policy development for behavioral conditions.

Towards medication-enhancement of cognitive interventions in schizophrenia

Current antipsychotic medications do little to improve real-life function in most schizophrenia patients. A dispassionate view of the dispersed and variable neuropathology of schizophrenia strongly suggests that it is not currently, and may never be, correctable with drugs. In contrast, several forms of cognitive therapy have been demonstrated to have modest but lasting positive effects on cognition, symptoms, and functional outcomes in schizophrenia patients. To date, attempts to improve clinical outcomes in schizophrenia by adding pro-cognitive drugs to antipsychotic regimens have had limited success, but we propose that a more promising strategy would be to pair drugs that enhance specific neurocognitive functions with cognitive therapies that challenge and reinforce those functions. By using medications that engage spared neural resources in the service of cognitive interventions, it might be possible to significantly enhance the efficacy of cognitive therapies. We review and suggest several laboratory measures that might detect potential pro-neurocognitive effects of drugs in individual patients, using a "test dose" design, aided by specific biomarkers predicting an individual's drug sensitivity. Lastly, we argue that drug classes viewed as "counter-intuitive" based on existing models for the pathophysiology of schizophrenia-including pro-catecholaminergic and NMDA-antagonistic drugs-might be important candidate "pro-cognitive therapy" drugs.

Understanding genetic risk for substance use and addiction: a guide for non-geneticists

There is considerable enthusiasm for the potential of genetics research for prevention and treatment of addiction and other mental disorders. As a result, clinicians are increasingly exposed to issues of genetics that are fairly complex, and for which they may not have been adequately prepared by their training. Studies suggest that the heritability of substance use disorders is approximately 0.5. Others report that family members of affected individuals experience a 4- to 8-fold increased risk of disorder themselves. Statements that addiction is "50% genetic" in origin may be taken by some to imply one's chances of developing the disorder, or that a lack of a positive family history confers immunity. In fact, such conclusions are inaccurate, their implications unwarranted given the true meaning of heritability. Through a review of basic concepts in genetic epidemiology, we attempt to demystify these estimates of risk and situate them within the broader context of addiction. Methods of inferring population genetic variance and individual familial risk are examined, with a focus on their practical application and limitations. An accurate conceptualization of addiction necessitates an approach that transcends specific disciplines, making a basic awareness of the perspectives of disparate specialties key to furthering progress in the field.

Paternal age and psychiatric disorders: findings from a Dutch population registry

BACKGROUND

We measured the association between paternal age and schizophrenia (SCZ), autism spectrum disorders (ASD), major depressive disorder (MDD), and bipolar disorder (BPD) in the Dutch population.

METHODS

In total, 14231 patients and 56924 matched controls were collected and analyzed for an association with paternal age by logistic regression.

RESULTS

ASD is significantly associated with increased paternal age: Older fathers >40 years of age have a 3.3 times increased odds of having a child with ASD compared to young fathers <20 years of age. SCZ has significant associations for fathers aged >35 years (OR=1.27, 95% Confidence Interval: 1.05 and 1.53). For MDD, both younger and older fathers have increased odds. No association was found for BPD.

CONCLUSIONS

The effects of paternal age as a risk factor are different for ASD and SCZ on one hand, and the affective disorders on the other hand. Different types of association might indicate different biological or psychosocial mechanisms. Late paternity (associated with predispositions to psychiatric disorders) seems the most probable explanation for the association with paternal age.

Annual Research Review: Transgenic mouse models of childhood-onset psychiatric disorders

Childhood-onset psychiatric disorders, such as attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), mood disorders, obsessive compulsive spectrum disorders (OCSD), and schizophrenia (SZ), affect many school-age children, leading to a lower quality of life, including difficulties in school and personal relationships that persist into adulthood. Currently, the causes of these psychiatric disorders are poorly understood, resulting in difficulty diagnosing affected children, and insufficient treatment options. Family and twin studies implicate a genetic contribution for ADHD, ASD, mood disorders, OCSD, and SZ. Identification of candidate genes and chromosomal regions associated with a particular disorder provide targets for directed research, and understanding how these genes influence the disease state will provide valuable insights for improving the diagnosis and treatment of children with psychiatric disorders. Transgenic mouse models are one important approach in the study of human diseases, allowing for the use of a variety of experimental approaches to dissect the contribution of a specific chromosomal or genetic abnormality in human disorders. While it is impossible to model an entire psychiatric disorder in a single mouse model, these models can be extremely valuable in dissecting out the specific role of a gene, pathway, neuron subtype, or brain region in a particular abnormal behavior. In this review we discuss existing transgenic mouse models for childhood-onset psychiatric disorders. We compare the strength and weakness of various transgenic mouse models proposed for each of the common childhood-onset psychiatric disorders, and discuss future directions for the study of these disorders using cutting-edge genetic tools.