Longitudinal studies on population representative samples offer unique insights. The Estonian Children Personality Behaviour and Health Study (ECPBHS; EstChild) was launched in 1998 on two birth cohort samples at age 9 or 15 with an exceptional participation rate, has been monitored at ages 15, 18, 25 and 33, and also recruited parents of the target subjects. This multidisciplinary investigation has been focused on behavioural neuroscience, illuminating findings on what could be discerned from biomarkers, candidate genes, gene × environment interactions, and epigenetic markers in representative samples, and in birth cohorts living through societal transformation. ECPBHS analysed how biomarkers and lifestyle are associated with real-life behaviours and developmental trajectories, phenotypes such as neuroticism, bulimia, aggressiveness or attention deficit, and outcomes from incidence of psychiatric disorders to the obtaining of university education. Novel evidence has been observed on clustering of fears and the inner structure of impulsivity and reward sensitivity, together with clues how these may have co-emerged with metabolic types. New insights have been provided to understand the classic biomarkers, cholesterol and platelet monoamine oxidase activity, as well as several functional gene variants. Hypotheses how to synthetise molecular genetics and sociology, how sex or gender matters in the light of gene × environment interactions and how family and parental roles shape the behaviour of offspring have been put forward. The ECPBHS has offered clues on why in biological psychiatry many replication attempts are predestined to fail, and how to learn from such failures.

Recent studies have suggested the involvement of brain RNA m(6)A methylation in stress response. One of the key players in the RNA m(6)A regulation is the demethylation catalysed by the fat mass and obesity-associated protein FTO, encoded by the fat mass and obesity-associated gene. Based on findings that experimental manipulation of the RNA m(6)A methylation in animal experiments can affect anxiety, and given that the C-allele of FTO rs1421085 had a significant association with indicators of overweight and obesity in our previous study, we have examined the possible association of FTO rs1421085 genotype with neuroticism in the same longitudinally observed sample. Data analysis included both birth cohorts of the Estonian Children Personality, Behaviour and Health Study (ECPBHS) that started in 1998/1999 when participants were 9 or 15 years old, respectively. Follow-ups were conducted at age 15, 18 and 25. Neuroticism at different ages was assessed with questionnaires of the five factor model. Statistically significant assocation between the FTO rs1421085 genotype and neuroticism emerged by age 25, with an additive effect of each T-allele. This association was largely based on females and was prominent in the older birth cohort at age 25, sampled during the Great Recession of 2007-2009. Conclusively, an overweight and obesity-related variant of FTO, the gene encoding an RNA m(6)A demethylase, was associated with lower neuroticism, this association being subject to gender and cohort effects.

Major vulnerability factors for psychiatric disorders such as depression, that often prevent complete remission and lead to relapses, are temperamental. In a rat model of clustered persistent high-anxiety/low-motivation, we have found that overexpression of glial cell line-derived neurotrophic factor (GDNF) by intra-striatally administered adeno-associated virus vector completely converts the passive coping style of low exploratory rats into an active one, similar to high exploratory rats. This conversion of the behavioural strategy developed gradually over repeated testing, and was associated with increased catecholamine metabolism in several brain regions and changes in the regulation of serotonin neurotransmission. An increase in dopamine transporter availability in the striatum was necessary for the phenotype conversion. Associated changes in striatal gene expression included key regulators of monoamine storage and epitranscriptomic regulation. The increase in GDNF signalling also caused alterations in levels and regional covariation of oxidative metabolism, suggestive of a reorganization of neural activity throughout the brain. Thus, neurotrophic factors, GDNF in particular, may play a pivotal role in the development, persistence and alteration of temperament/personality traits, and therefore constitute a potential target for treatment of chronic, relapsing psychiatric disorders.

Tryptophan hydroxylase 2 (TPH2), the rate-limiting enzyme of serotonin synthesis in the CNS, has been associated with numerous behavioural traits and psychiatric disorders. Tph2 modified mice present altered sensitivity to stress, and excessively aggressive behaviour that develops even in female animals. We have measured histochemically the activity of cytochrome c oxidase (COX) in 106 brain regions in wildtype, Tph2 heterozygous and total knockout male and female mice (n=78). In addition to direct comparisons by sex and genotype, COX activity co-variation in putative aggression networks was examined. Overall, female mice have higher COX activity than males. In regions affected by Tph2 inactivation a consistent pattern emerged, where Tph2± mice had the lowest, Tph2−/− mice had the highest COX activities, and Tph2+/+ in-between. Tph2 inactivation induced broad changes and an extensive reorganisation of neural activity as revealed by regional activity co-variation matrices of COX. These patterns of inter-regional correlations differed between sexes. Co-variation of COX activity also differed between males and females in the proposed networks for aggressiveness. In male mice, Tph2 inactivation disrupted co-variation of COX activity of the dorsal raphe and the periaqueductal grey matter with limbic regions. The septum appears as a hub of altered connectivity in females but not in males. Serotonin deficiency is associated with altered regional neural activity patterns as revealed by COX histochemistry. These alterations are profoundly different in male and female mice, and suggest that serotonin plays a partly sex-dependent role in the regulation of behaviour.

BACKGROUND AND AIMS:Separate birth cohorts experience different social and environmental factors, which may lead to differences in psychological and social development and health-related behaviours. We analysed the association between age, birth cohort and body weight, glucose metabolism, diet, and cardiorespiratory fitness (CRF). METHODS AND RESULTS:The sample included two very similarly formed birth cohorts (n = 1238) of the Estonian Children Personality Behaviour and Health Study. Body weight, diet and CRF from 15 to 25 years was analysed by birth cohort using the linear mixed-effects regression model. Differences at ages 15, 18, and 25 years were assessed by independent group t-test. Prevalence of overweight and obesity increased over time across both birth cohorts and sexes. Subjects from the older birth cohort had lower measures of obesity at ages 15 and 18 years. However, in males, the difference either disappeared or was reverse by age 25. The increase per year in measures of obesity was significantly greater among subjects in the older birth cohort, compared to the younger cohort. The older birth cohort had higher daily energy intake (kcal) at ages 15 and 25 years and higher carbohydrate intake (g) at ages 15, 18 and 25 years. CONCLUSION:During profound societal changes, birth cohort effects on body weight and weight gain can rapidly emerge, with sex differences. Relationship between birth cohort and measures of obesity may at least partly be driven by energy intake, especially from carbohydrates.

Rewards are rewarding owing to their hedonic or metabolic value. Individual differences in sensitivity to rewards are predictive of mental health problems but may reflect variation in metabolic types. We have assessed the association of two distinguishable aspects of reward sensitivity, openness to rewards (the striving towards multiple rewards) and insatiability by reward (the strong pursuit and fixation to a particular reward), with measures of metabolism and activity in a longitudinal study of representative birth cohort samples. We used data of the Estonian Children Personality Behaviour and Health Study (original n = 1238) collected at age 15, 18 and 25. Reward sensitivity and physical activity were self-reported during a laboratory visit, when also blood sampling, measurement of blood pressure, height and weight, aerobic exercise testing and the diet interview, after the participants had kept food diary, took place. In the younger cohort, physical activity was also assessed by accelerometry at age 18 and 25. Across adolescence and young adulthood, openness to rewards was positively associated with physical activity and negatively with blood pressure and serum levels of glucose, insulin and cholesterol levels. In contrast, insatiability by reward was positively associated with serum triglyceride levels and negatively with energy intake and cardiorespiratory fitness. In conclusion, the two facets of reward sensitivity have a fairly different association with a variety of metabolic and health-related measures. This may explain the variable findings in literature, and suggests that individual differences in reward sensitivity are part of a complex physiological variability, including energy expenditure profiles.

Stress contributes to the development of psychiatric disorders. We have previously shown that rats with low inherent positive affectivity, assessed by 50-kHz ultrasonic vocalizations (USV), are more vulnerable to stress, and that free-fed rats with persistently lower consumption of sucrose are less sensitive. Hence we compared the association of these traits with the effect of chronic stress within a single experiment. Male Wistar rats were classified as of high (HC) or low (LC) positive affectivity based on their average 50-kHz USV response, and as young adults the rats were further divided into high and low sucrose-consuming (HSuc and LSuc, respectively). Four groups comprising twenty rats each were formed, and half of the animals submitted to chronic variable stress (CVS) for 5 weeks. CVS was followed by behavioural tests and ex vivo biochemical analyses. In elevated plus-maze, CVS increased the anxiety-related measures most prominently in the LC-HSuc rats. Stress reduced amphetamine-induced 50-kHz USVs statistically significantly only in LC-HSuc rats. Serum glucose and adrenal weight, as well as levels of monoamines and their metabolites in the frontal cortex, striatum, nucleus accumbens, amygdala and hypothalamus, were altered by chronic stress mostly in a phenotype-dependent manner. CVS also increased 5-HT2 C-receptor gene expression in the striatum of LC-HSuc rats. Conclusively, previous separate findings that individual differences in positive affectivity and sucrose intake (hedonic response) can contribute to stress vulnerability were confirmed. Importantly, the highest vulnerability to stress was found if low positive affectivity and high sucrose consumption coincided.

Objective: Ultrasonic vocalisations (USVs) emitted by rats may reflect affective states. Specifically, 50 kHz calls emitted during juvenile playing are associated with positive affect. Given that depression is characterised by profound alterations in this domain, we proposed that USV calls may configure a suitable tool for assessing depressive-like states. Utilising the Flinders Sensitive Line (FSL), a well-established animal model of depression, we assessed USV calls emitted by rats during tickling, a procedure based on juvenile rats' rough-and-tumble play.Methods: Juvenile FSL rats and their control counterparts, the Flinders Resistant Line (FRL) and Sprague Dawley, were submitted to tickling sessions to imitate rats playing behaviour. The rats were tickled daily for 6 weeks starting at PND21. Tickling sessions were recorded for further acoustic analysis of 50 kHz calls.Results: Tickling increased 50 kHz calls in all the strains. FSL rats emitted more calls than control strains and exhibited a higher number of flat-trill combination calls.Conclusion: Tickling is a robust method for inducing 50 kHz USV calls. Analysing USV calls emitted during tickling configurates a suitable method for studying affective states relevant to depression. FSL rats did not present anhedonia but rather higher reward sensitivity, which may underlie their stress vulnerability.

Aggression constitutes a significant behavioral issue associated with delinquent behavior, commonly observed in youth diagnosed with conduct disorder (CD) and living in correctional facilities. Catechol-o-methyl-transferase (COMT) gene variants modify the environmental sensitivity associated with the risk of aggression. This study evaluated the association of COMT rs4680 and rs4818 polymorphisms with aggressive behavior in 341 male adolescents living inside and outside a correctional facility, with or without a diagnosis of CD. Aggression was assessed using the Hare Psychopathy Checklist: Youth Version (PCL-YV), Modified Overt Aggression Scale (MOAS) and Swanson, Nolan and Pelham Questionnaire. COMT rs4680 and rs4818 polymorphisms were genotyped using TaqMan SNP Genotyping Assays. A similar prevalence of the COMT genotypes or haplotypes was found between adolescents with or without CD, suicidal behavior, or detention in correctional facility. In youth with CD, the COMT rs4680 A allele was associated with higher MOAS verbal aggression, aggression toward objects, irritability (subjective and open), and PCL-YV interpersonal domain scores compared with carriers of the COMT rs4680 G allele. COMT rs4818 GC carriers with CD had higher scores on the MOAS subjective irritability than GG heterozygotes. These novel findings revealed the association of lower COMT rs4680 and rs4818 activity alleles with aggression in detained male adolescents with CD.

Major vulnerability factors for psychiatric disorders such as depression, that often prevent complete remission and lead to relapses, are temperamental. In a rat model of clustered persistent high anxiety/low motivation, we have found that overexpression of glial-cell-line-derived neurotrophic factor (GDNF) by intra-striatally administered adeno-associated virus vector strikingly converts the passive coping style of low exploratory rats into an active one, similar to high exploratory rats. This conversion of behavioural strategy developed gradually over repeated testing, and was associated with increased catecholamine metabolism in several brain regions and changes in the regulation of serotonin neurotransmission. An increase in in vivo dopamine transporter availability in the striatum was necessary for the phenotype conversion. Associated changes in striatal gene expression included key players in monoamine storage and epitranscriptomic regulation. The increase in GDNF signalling also caused alterations in levels and regional covariation of oxidative metabolism, indicative of persistent reorganization of neural activity throughout the brain. Thus, neurotrophic factors, GDNF in particular, may play a pivotal role in the development, persistence and alteration of personality traits, and therefore constitute a potential target for treatment of chronic, relapsing psychiatric disorders. ### Competing Interest Statement The authors have declared no competing interest.

Objective Lower platelet monoamine oxidase (MAO) activity has consistently been associated with excessive risk-taking and general psychiatric vulnerability. How this peripheral measure can represent presumably centrally regulated complex behaviours is not clear but platelet MAO activity has been suggested to reflect the capacity of serotonin release in the brain. Secretion of prolactin is in part under serotonergic control and indicates serotonin release capacity. Methods We have assessed release of prolactin and other exercise-induced hormones in response to strenuous physical exercise in twenty male subjects and examined its association with platelet MAO activity as measured radioenzymatically. Results Increase in prolactin levels was positively correlated with platelet MAO activity. Levels of cortisol, growth hormone and aldosterone were also raised by exercise, but these increases were not associated with platelet MAO activity. Unexpectedly, aldosterone levels before exercise were also in a positive correlation with platelet MAO activity. Conclusion The finding that exercise-induced prolactin release is associated with MAO activity in platelets indirectly supports the notion that platelet MAO activity is a marker of central serotonin release capacity.

BACKGROUND:Social behaviour is the expression of one of the most generally accepted independent dimensions of personality. Serotonergic neurotransmission has been implicated in typical social response and drugs that promote serotonin (5-hydroxytryptamine (5-HT)) release have prosocial effects. By using the social interaction test, we have previously demonstrated sociability as a temperamental trait in male Wistar rats. AIMS:To assess sociability in male rats of the Sprague-Dawley strain and in female rats of both Wistar and Sprague-Dawley strain, and extracellular levels of 5-HT in rats with high and low sociability (high sociability (HS)- and low sociability (LS)-rats). METHODS:Social interaction test conducted with different weight-matched partners was used to assess sociability, and in vivo, microdialysis was performed before and after administration of a low dose (2 mg/kg) of parachloroamphetamine (PCA) in the prefrontal cortex, dorsamedial striatum and ventral tegmental area. RESULTS:Similarly to male Wistar rats, female Wistars and Sprague-Dawley rats of both sexes displayed trait-wise sociability. Male Wistar HS-rats had lower extracellular levels of 5-HT in prefrontal cortex at baseline and after administration of PCA, and higher PCA-induced increase of extracellular 5-HT in ventral tegmental area. In dorsomedial striatum, PCA elicited a comparable increase in extracellular dopamine in HS- and LS-rats, but higher release of 5-HT in HS-rats. Comparison of PCA-induced 5-HT release in prefrontal cortex of male and female Sprague-Dawley rats revealed a larger 5-HT response in female HS-rats. CONCLUSIONS:5-HT release potential is higher in rats with high expression of sociability trait, whereas some regionally variable differences may be related to relative contributions of social motivation and anxiety in shaping social behaviour.

Introduction: The role of catechol-O-methyltransferase (COMT) in catecholamine neurotransmitter metabolism has led to the investigation of variants of the corresponding gene in the etiology of different psychiatric disorders, but the results are inconclusive. Methods: We have examined the relationship between COMT Val158Met single nucleotide polymorphism (rs4680) and the occurrence of psychiatric disorders in a highly representative birth cohort sample of young adults in the Estonian Children Personality Behaviour and Health Study (original n = 1,238). The lifetime occurrence of psychiatric disorders at the age of 25 years was assessed with the Mini-International Neuropsychiatric Interview. Results: Both Val- and Met-alleles of the COMT Val158Met were associated with specific psychiatric disorders. Met-allele carriers had a significantly higher occurrence of agoraphobia (3.2% vs. 0.5%; χ2 = 4.10; p < 0.05) compared to Val/Val homozygotes. Also, the occurrence of panic disorder was significantly higher in female Met-allele carriers than in Val/Val homozygote females (10.2% vs. 3.6%; χ2 = 4.62 p = 0.03). In contrast, the occurrence of generalized anxiety disorder was higher in Val/Val females when compared to Met-allele carriers (12.7% vs. 6.8%; χ2 = 4.16; p = 0.04). Also, female Val/Val homozygotes (15.5%) had a higher occurrence of eating disorders than Met-allele carriers (6.1%) of the COMT Val158Met polymorphism (χ2 = 10.39; p = 0.002). In the whole sample, Met-allele homozygotes had a higher occurrence of alcohol use and substance use disorders than Val-allele carriers (χ2 = 3.62 and 3.68, respectively; p < 0.05). Conclusion: In a regional highly birth cohort representative sample, either COMT rs4680 variant was observed in association with specific psychiatric disorders.

Road traffic injuries are the leading cause of death for young adults, and parents play a major role in shaping their traffic behaviour. Higher impulsivity (predictor of higher traffic risk) has been shown to be dependent on family relations and the serotonin transporter gene promoter polymorphism (5-HTTLPR). The specific mechanisms for the inheritance of risky traffic behaviour from parents to children are not clear, and the genetic aspect has not been studied before. We used data of Estonian Children Personality Behaviour and Health Study subjects (n = 596, mean age = 25.2 ± 0.6) and their parents (mothers, n = 460, mean age = 52.1 ± 5.8; fathers, n = 339, mean age = 54.1 ± 6.5). Family relationships scale, traffic risk questionnaires and Adaptive and Maladaptive Impulsivity Scale were filled out. The increased risk-taking behaviour of parents and worse quality of family relationship were significant predictors of higher traffic risk among subjects. Family support and impulsivity of fathers significantly predicted the subjects’ traffic risk score in interaction with 5-HTTLPR genotype: l’/l’ homozygous subjects with adaptively impulsive fathers had higher traffic risk, whereas for s’-allele carrying subjects family support was more significant. Parental role modelling and family relationships are significant predictors of future traffic behaviour of the child. Whether the behavioural example of the father or the influence of family relationships is more important in predicting future risky traffic behaviour, depends on the 5-HTTLPR genotype of the child.

OBJECTIVE:Neuropeptide Y (NPY) is a powerful regulator of anxious states, including social anxiety, but evidence from human genetic studies is limited. Associations of common gene variants with behaviour have been described as subject to birth cohort effects, especially if the behaviour is socially motivated. This study aimed to examine the association of NPY rs16147 and rs5574 with personality traits in highly representative samples of two birth cohorts of young adults, the samples having been formed during a period of rapid societal transition.METHODS:Both birth cohorts (original n = 1238) of the Estonian Children Personality Behaviour and Health Study (ECPBHS) self-reported personality traits of the five-factor model at 25 years of age.RESULTS:A significant interaction effect of the NPY rs16147 and rs5574 and birth cohort on Agreeableness was found. The T/T genotype of NPY rs16147 resulted in low Agreeableness in the older cohort (born 1983) and in high Agreeableness in the younger cohort (born 1989). The C/C genotype of NPY rs5574 was associated with higher Agreeableness in the younger but not in the older cohort. In the NPY rs16147 T/T homozygotes, the deviations from average in Agreeableness within the birth cohort were dependent on the serotonin transporter promoter polymorphism.CONCLUSIONS:The association between the NPY gene variants and a personality domain reflecting social desirability is subject to change qualitatively in times of rapid societal changes, serving as an example of the relationship between the plasticity genes and environment. The underlying mechanism may involve the development of the serotonergic system.

ABSTRACT Background The study aims to explore the potential antianxiety effect of Froriepia subpinnata, a native plant in northern Iran, and it is considered an antiflatulent, appetizing, antiseptic, antispasmodic, and diuretic. Despite its widespread use in diets and its reputation for calming effects, no prior research has specifically investigated its antianxiety properties. Methods Rats were subjected to a variety of stressors for 24 days. Rats were treated with the F. subpinnata extract (100, 200, and 400 mg/kg, orally) for 14 days starting from the 10th day of stress. Then behavioral tests (elevated plus‐maze, open field, sucrose preference, Morris water maze, passive avoidance) were examined. Real‐time PCR was used to investigate changes in the expression of candidate genes of stress response and memory. Oxidative stress markers and corticosterone levels in serum were also measured. Results Chronic stress reduced performance in a variety of tests of anxiety and memory, and treatment with the F. subpinnata extract dose‐dependently improved the behavioral deficits caused by chronic stress. At the dose of 200 mg/kg, the F. subpinnata extract mitigated the effect of stress on the expression of several genes, such as those encoding dopamine D1 and D2 receptors, glutamate NMDA, and AMPA receptor subunits (Grin1 and Gria1, respectively), glucocorticoid and mineralocorticoid receptors, cholecystokinin (CCK) and CCKB receptor, neuropeptide Y, and the GABAA receptor alpha2 subunit. Also, the expression of two genes, TrkB and BDNF, was significantly affected by the extract, demonstrating meaningful decreasing changes. Furthermore, treatment with the extract led to a decrease in oxidative stress and an elevation in cortisol levels in stressed animals. Conclusion In this study, we provide the first evidence of the antistress and antianxiety effects of F. subpinnata extract, along with its potential procognitive impact on memory.