Recent decreasing trend in U.S. juvenile delinquency attributable to changes in maternal age

Two documented associations, viz., a negative one between maternal age and externalizing behavior of the offspring and a positive one between externalizing behavior in childhood and the probability of later (juvenile) delinquency, lead to the prediction that cohort-changes in crime rate over the years are associated with the age of the mothers of these cohorts when the children were born. This prediction was tested by comparing U.S. crime figures between 1987 and 1997 with maternal age figures 17 years earlier (1970-1980). Both time series show a close resemblance. Although causality from two different time series cannot be asserted, the existence of such a relationship is made plausible. Two different hypotheses are presented about the possible nature of causality. Results may be of value for studies in crime epidemiology.

Interictal and postictal cognitive changes in migraine

The question whether symptom-free migraine patients show cognitive impairments compared to matched control subjects is addressed, and also whether migraine patients show transient cognitive impairments induced by an attack. The Neuropsychological Evaluation System (NES2) was administered once in an interictal period and twice within 30 h after different migraine attacks. Since cognitive impairments could be related to attack duration or severity, cognitive performance was compared during a postictal period after sumatriptan use and during a postictal period after habitual nonvasoactive medication use. Twenty migraineurs without aura, 10 migraineurs with aura, and 30 matched headache-free controls participated in the study. During a headache-free period, migraineurs without aura responded as quickly as controls, while migraineurs with aura were slower than controls during all tasks specifically requiring selective attention. These effects were not aggravated by a preceding migraine attack, irrespective of medication use and attack duration.

Child behavior problems increased by maternal smoking during pregnancy

We investigated the effects of maternal smoking during pregnancy on behavioral problems (i.e., not mediated by low birth weight) in 3-y-old offspring. We assessed behavioral problems in 1377 2- to 3-y-old twin pairs (registered in the Netherlands Twin Register) with the Child Behavior Checklist for ages 2-3 y (CBCL/2-3) from Achenbach, Edelbrock, and Howell. Two to 3 y earlier (i.e., soon after the birth of the twins) we collected information about the smoking habits (i.e., "never," "sometimes," and "regularly") of the mother during pregnancy. We analyzed the effect of maternal smoking on the CBCL total score and on several subscale scores for first- and second-born twins separately, and we adjusted for the possible confounding effects of birth weight, socioeconomic status, maternal age, and type of feeding (i.e., breast or bottle fed). There was a significant effect of maternal smoking on so-called "externalizing" behavioral problems (e.g., oppositional, aggressive, overactive), but not on "internalizing" behavioral problems (e.g., withdrawn, depressed, anxious), in both first- and second-born twins. The enhanced "externalizing" problems were attributed predominantly to increased aggression. Although boys have higher externalizing and aggression scores than girls, the effect of maternal smoking was the same for boys and girls.

Cognition in children does not suffer from very low lead exposure

We studied the relationship between exposure to lead and memory and attention in children. Participants were 313 boys aged 9 to 12 years who attended special education schools in the Netherlands. Children whose possible attentional or memory problems were obviously due to causes other than lead contamination were excluded from the study. Cognition was assessed by extensive theory- based testing. Blood lead concentration was measured to assess body lead burden. Possible confounding factors that might affect blood lead level and/or cognitive functioning were assessed. Blood lead levels were higher in children with lower socioeconomic status and in children with more hand-to-mouth behavior, and varied seasonally, with higher values in spring and summer. The mean blood lead level was 44.4 microgram lead per liter blood, which is considered low. Only 2% of the children showed a slightly higher blood lead level than the American safety standard. To obtain robust measures of cognitive aspects, we performed a factor analysis. The results showed that blood lead level did not influence any of the cognitive factors. Therefore this study, despite being designed to maximize the chance of finding an effect in asymptomatic children, does not support a relationship between lead at very low doses (below 100 micrograms/liter blood) and cognition in schoolchildren.

Frequency of parental report of problem behavior in children decreases with increasing maternal age at delivery

Child behavior problems were assessed in 1377 3-yr.-old twin pairs with the Child Behavior Check List from Achenbach (translated into Dutch language by Verhulst). The association between problem scores and maternal age at delivery of the twins was analyzed with statistical control for several potential confounding variables: birth weight of twins, maternal smoking during pregnancy, being breast or bottle fed and socioeconomic status. After controlling for all available confounding covariates, a significant linear effect for maternal age was left. Especially Externalizing behavior problems as well as the separate categories that constitute Externalizing, i.e., Aggressive, Oppositional, and Overactive, appeared to decrease continuously with increasing maternal age. This was true for both boys and girls as well as for first and secondborn twins. Evidence in support of a biological explanation of the association between maternal age and child behavior problems, is presented.

Increase in child behavior problems resulting from maternal smoking during pregnancy

In this article, the authors investigated the effect of maternal smoking during pregnancy on behavioral problems, which were not mediated by lower birth weight, in offspring at 3 y of age. The authors used the Child Behavior Checklist for ages 2-3 y (CBCL/2-3; Achenbach, Edelbrock and Howell) to assess behavioral problems in 1,377 2- to 3-y-old healthy twin pairs. Soon after the birth of twins, the authors collected pre- and perinatal information, including smoking habits of the mother during pregnancy. The question "Did you smoke during pregnancy?" could be answered by choosing one of three possible options: (1) never, (2) sometimes, or (3) regularly. The authors analyzed the effect of maternal smoking on the Child Behavioral Checklist total score and on several subscale scores for first- and second-born twins separately, and they adjusted for the possible confounding effects of birth weight, socioeconomic status, maternal age, and having been breast- or bottle-fed. There was a significant effect of maternal smoking on so-called externalizing behavior problems (oppositional, aggressive, overactive), but not on internalizing behavior problems (withdrawn, depressed, anxious), in both first- and second-born twins. The authors primarily attributed the enhanced externalizing problems to increased aggression. Although boys had higher externalizing (and aggression) scores than girls, the effect of maternal smoking was the same for boys and girls. The authors also discuss whether maternal smoking causes externalizing behavior problems.

Cardiovascular response to physical stress in offspring of hypertensive parents: Dutch Hypertension and Offspring Study

Blood pressure (BP) regulatory mechanisms were studied in youngsters with contrasting risks for hypertension, based on parental history, during physical stress. As a static exercise, an isometric handgrip task (22% of maximal force during 5 min) was used and a dynamic exercise task was performed on a bicycle ergometer. At rest and during stress, BP and heart rate were recorded. In order to study the adaptation of the cardiovascular system to physical stress, cardiac output and total peripheral resistance were measured in addition to indices of vagal and sympathetic influences on the heart. Heart rate and cardiac output declined significantly more in offspring of hypertensive parents during static exercise (difference in heart rate: -2.5 +/- 1.2 bpm, P = 0.04; difference in cardiac output: -9.0 +/- 4.6%, P = 0.05). This is most likely the result of a larger increase in the total peripheral resistance in youngsters at risk (difference: 13.2 +/- 6.8%, P = 0.06). No differences between the two groups were found in reactivity of BP or in the indices of sympathetic activation or vagal inhibition of the heart. The offspring of hypertensive parents showed an attenuated increase in stroke volume during the dynamic exercise task (difference at the first cycling level: -11.5 +/- 5.4%, P = 0.04), while no difference in neural activity or heart rate was found. Youngsters with a parental history of hypertension show an enhanced reactivity of total peripheral resistance during static exercise. This does not lead to a higher BP response in this group, most probably because of a larger decrease of the cardiac output. During dynamic exercise the physiological increase in stroke volume is blunted in offspring of hypertensive parents.

Left-handedness in twins: genes or environment?

Twin family data can cast light on the longstanding problem about the influences of genes and environment on the etiology of left-handedness. Therefore, hand preference was assessed in 1700 adolescent twin pairs and their parents. Left-handedness (LH) appeared not significantly enhanced among twins compared to the general population. In addition the following observations were made: (1) Significant more LH in first born twins than in second born twins. (2) Significant higher left-handedness association in MZmm pairs compared to DZmm pairs and not or may be marginally so in MZff versus DZff pairs. These results, combined with the observations that (a) left-handed fathers increase the probability of LH in sons but not in daughters; (b) LH in mothers increases LH prevalence in both sons and daughters to the same degree; and (c) very low birth weight, corrected for the effect of gestational age, increases LH prevalence in first born twins only, make an environmental explanation more likely. The possibility that exposure to prenatal male hormones - to which low birth weight and high birth stress children are more vulnerable - might be a crucial condition for the etiology of LH, is discussed.

Genetic modelling of dizygotic twinning in pedigrees of spontaneous dizygotic twins

The inheritance of spontaneous dizygotic (DZ) twinning was investigated in 1,422 three-generation pedigrees ascertained through mothers of spontaneous DZ proband twins. DZ twinning was modelled as a trait expressed only in women. The penetrance was modelled first as a parity independent and secondly as parity dependent. The observed frequencies of maternal and paternal grandmothers with DZ twins differed significantly from the expectations under an X-linked mode of inheritance. Complex segregation analysis showed that the parity-independent phenotype of "having DZ twins" was consistent with an autosomal monogenic dominant model, with a gene frequency of 0.035 and a female-specific lifetime penetrance of 0.10. Recessive, polygenic, and sporadic models were rejected. The autosomal dominant model revealed a strong robustness against a changing population prevalence and the loss of information due to the presence of same-sexed twin pairs of unknown zygosity. When DZ twinning was modelled as a parity dependent trait, the data were compatible with an autosomal dominant model with a gene frequency of 0.306 and a penetrance of 0.03 per birth for female gene carriers.

Pupillometric assessment of compensatory effort in a memory search task under physical and pharmacologically-induced suboptimal states

Extensive research has shown that the phasic pupil size (peak level on each trial) is a sensitive measure of the degree of mental effort demanded by a task. In the present study, the validity of the pupil response as an index of mental effort in suboptimal conditions was investigated. Thirteen males (19-29 years) performed a memory and display-search task in a practice session, followed in random order by an oxazepam session, a placebo session, a physical exercise session, and a control session. After both oxazepam and physical exercise, decision times increased, but pupil response increased only after physical exercise. This result was explained by the possibility that under physical fatigue, compensatory effort was exerted, whereas under drug-induced fatigue, subjects seemed unable to compensate for the performance decrement. The pupil response appears to be a valuable tool for gaining more insight into different effects of suboptimal states.

Cardiovascular response to mental stress in offspring of hypertensive parents: the Dutch Hypertension and Offspring Study

OBJECTIVE

To compare blood pressure-regulating mechanisms during mental stress in two groups of offspring with contrasting risk for hypertension.

DESIGN

Cardiovascular reactivity to two different types of mental stressors was studied in adolescents and young adults with two hypertensive or two normotensive parents. The two tasks used were intended to evoke either a predominantly adrenergic cardiac response (a memory search task) or a predominantly vascular response (a reaction-time task with visual search and tone avoidance).

METHODS

Blood pressure and heart rate were recorded at rest and during stress. To study adaptations of the cardiovascular system to mental stress, cardiac output, total peripheral resistance and indices of vagal and sympathetic influences on the heart were measured.

RESULTS

The reactivity of systolic blood pressure (SBP) to the memory search task was significantly higher in offspring of hypertensive parents, which resulted in a longer recovery after the task. In contrast, during the reaction-time task, offspring of hypertensive parents had a significantly enhanced reactivity of peripheral resistance, but no differences in heart rate or blood pressure response were observed. No differences between the two groups were found in sympathetic or vagal activity during either task measured by the ratio of pre-ejection time and left ventricular ejection time, and respiratory sinus arrhythmia, respectively.

CONCLUSION

Apart from a higher reactivity of SBP during the memory search task, no other indications supporting the presence of hyperadrenergic activation of the heart in early primary hypertension were found. On the contrary, the results of the present study support the hypothesis that blood pressure responses in prehypertensive subjects are characterized by enhanced vasoconstriction rather than by increased cardiac output.

A twin-singleton comparison of problem behaviour in 2-3-year-olds

Twin-singleton differences in problem behaviours in 2-3-year-olds were studied. Maternal ratings of children's problem behaviours were obtained with the CBCL/2-3. The twin sample consisted of 1363 twin pairs (456 MZ, 907 DZ), the sample of singletons consisted of 420 children from the general population. Results indicated that the general level of problem behaviours in twins was broadly comparable to that in singletons. Four of the seven syndromes showed lower scores for twins. These differences, however, were small and mainly caused by lower scores for DZ twins in comparison to MZ twins and singletons. Part of the difference could be attributed to the higher maternal age in the twin groups. Higher means for boys were found for the total problem score, and the Aggressive and Overactive syndromes.

Effect of maternal smoking on birth weight of twins: a study from the Dutch Twin Register

Since twins weigh about 20% less than singletons at birth, maternal smoking may be a more severe risk for them than for singletons. Therefore, the effect of maternal smoking during pregnancy on birth weight was investigated in a group of 5376 twins. All necessary information was collected by a questionnaire filled out by the mother of the twins. Gestational age explains more than 75% of the variance in birth weight. Other effects were tested with gestational age as a covariate. Apart from zygosity (DZ twins weigh more than MZ twins), birth order (first born twins weigh more than second born twins) and sex (boys weigh more than girls), there was a very significant birth weight reducing effect (more than 8%) maternal smoking as well as a significant influence of maternal age (young mothers give birth to smaller children). There were no interactions with maternal smoking.

Exposure to lead and specific attentional problems in schoolchildren

A pilot study was carried out to investigate the relationship between exposure to lead and attention in children. The participants were 43 boys, 8 to 12 years of age, attending special schools for children with educational and/or learning problems (so called LOM schools). Children with probable causes of attentional or memory problems other than lead contamination were excluded from the study. Various aspects of attention were measured using neuropsychological tests. As an assessment of body lead burden, lead concentration in the boys' hair was measured by means of the Synchrotron Radiation-Induced X-ray Fluorescence technique (SXRF). Information was collected about variables that possibly could influence attention and/or body lead burden (confounding factors). A multiple regression analysis was used to determine the contribution of lead to variance in performance, after correction for confounding factors. The results showed that children with relatively high concentrations of lead in their hair reacted significantly slower in a simple reaction-time task than did children with relatively low concentrations of lead in their hair. In addition, the former were significantly less flexible in changing their focus of attention, even after correction for the influence of their delayed reaction time.

Anthropometric measures, fitness and habitual physical activity in offspring of hypertensive parents. Dutch Hypertension and Offspring Study

As part of the Dutch Hypertension and Offspring Study, subjects with contrasting risk for hypertension according to their parental history of hypertension were compared with respect to anthropometric measures and measures of fitness and physical activity. Body height, weight, two skinfolds, and blood pressure at rest were measured. Fitness was evaluated by a maximal exercise test, and habitual physical activity was assessed using a questionnaire. No differences were observed in body mass index after adjustment for slight differences in age and proportion of men between the groups (difference between groups: 0.74 kg/m2, 95% CI: -0.30, 1.78). Offspring of hypertensive parents, however, had significantly more central fat (difference between groups: 2.32 mm, 95% CI: 0.18, 4.46). No differences in fitness or physical activity were present between the two groups. The results of this study indicate a potential role for central fat in the etiology of primary hypertension. Fitness or habitual physical activity are, however, not different between groups of subjects at different risk for future hypertension.

Genetic and social influences on starting to smoke: a study of Dutch adolescent twins and their parents

In a study of 1600 Dutch adolescent twin pairs we found that 59% of the inter-individual variation in smoking behaviour could be attributed to shared environmental influences and 31% to genetic factors. The magnitude of the genetic and environmental effects did not differ between boys and girls. However, environmental effects shared by male twins and environmental effects shared by female twins were imperfectly correlated in twins from opposite-sex pairs, indicating that different environmental factors influence smoking in adolescent boys and girls. In the parents of these twins, the correlation between husband and wife for 'currently smoking' (r = 0.43) was larger than for 'ever smoked' (r = 0.18). There was no evidence that smoking of parents (at present or in the past) encouraged smoking in their offspring. Resemblance between parents and offspring was significant but rather low and could be accounted for completely by their genetic relatedness. Moreover, the association between 'currently smoking' in the parents and smoking behaviour in their children was not larger than the association between 'ever smoking' in parents and smoking in their children.

Effect of tyrosine on cognitive function and blood pressure under stress

The effects of tyrosine on mood, performance, heart rate and blood pressure of 16 healthy young subjects were assessed. Subjects were tested on two separate days, one test session after ingestion of 100 mg/kg tyrosine and the other test session after placebo, in random order. While performing a number of stress sensitive tasks, subjects were exposed to a stressor consisting of 90 dB noise. Tyrosine was found to improve the performance on two cognitive tasks, which were performed 1 h after administration of the medication and which could be characterized as highly sensitive to stress. In addition, tyrosine decreased diastolic blood pressure 15 min after ingestion, while 1 h after ingestion diastolic blood pressure was the same with tyrosine and placebo. No effects on mood, systolic blood pressure and heart rate were found.

Effects of behavioral psychophysiological treatment on schoolchildren with migraine in a nonclinical setting: predictors and process variables

Evaluated the outcome of a combined behavioral therapy, comprising relaxation training, temperature biofeedback, and cognitive training, administered in a school setting, at posttreatment, and 7-month follow-up, on a group of schoolchildren with migraine. Comparison between the experimental group (n = 32) and the waiting-list control group (n = 9) showed a treatment effect on headache frequency and duration but not on intensity. Using a 50% reduction in the headache activity as a criterion for clinical improvement, 45% of the children in the experimental group were clinically improved at the end of the treatment. The treated subjects were found to have maintained significant improvement at follow-up. Sex, headache history, age, and psychosomatic complaints before the training emerged as predictors of outcome. A decrease in state anxiety and an increase in the ability to relax during the sessions contributed to headache improvement. Finally, the acquired capacity to raise one's finger temperature during the biofeedback sessions was related to headache reduction after the training.

Brain potential differences related to spatial attention in migraineurs with and without aura symptoms support supposed differences in activation

It is to be expected that differences in electrical activity of the brain between migraine patients with aura and those without aura can only be revealed by stimuli that provoke visual spatial processing, i.e. stimuli that trigger so called endogenous Visual Evoked Potential (VEP) activity. This is not the case for the flashes and checkerboard reversals. Those stimuli elicited exogenous activity only. During and between attacks the blood flow of migraineurs with aura changes in the posterior cerebral part of the brain, which is assumed to be specialized in the processing of spatial aspects of visual stimuli. Reaction times (RTs), early and late Event Related Potential (ERP) differences were compared at 12 scalp positions for two groups of migraineurs (with and without aura) and a control group. They had to perform a passive attention task, checkerboard reversals, and an active attention task, where attention was either divided into or focussed at spatial locations. In agreement with many studies on migraine, checkerboard stimuli did not differ on any early components. However, RTs were faster for migraineurs with aura and their early components were different when stimuli were highly attended. This is probably because these stimuli can relatively easily trigger cortical activity due to an over activated central mechanism and an enhanced level of attention.

Adrenaline and the relationship between neurosomatism, aerobic fitness and mental task performance

The influence of neurotic instability as manifested by functional somatic complaints (neurosomatism) and aerobic fitness on responses to mental stress and to intravenous adrenaline infusions were investigated in 44 university students. Adrenaline-induced changes from resting levels in state anxiety and somatic anxiety were significantly more pronounced in high than in low neurosomatic subjects and all anxiety ratings were generally negatively related to aerobic fitness. Cardiovascular reactivity was induced by mental stress and by adrenaline infusions, but was not altered by neurosomatism. In individuals assumed to be characterized by a susceptibility to adrenergic effects, interference of adrenaline-induced arousal with cognitive performance may not occur. In contrast, a further increase in performance may occur when adrenaline is infused. Performance measures correlated negatively with anxiety during the baseline task and the placebo task, but this negative relation was absent during the adrenaline infusion and was replaced by positive relations between performance and aerobic power. The complex relations between bodily symptoms of anxiety, aerobic fitness and mental stress are discussed.

Effect of depression on psychomotor skills, eye movements and recognition-memory

In this study 12 depressed outpatients were compared to 12 healthy controls with respect to their performance on a number of cognitive tasks, including a recognition-memory task, and their eye movements and pupil size were recorded while watching a traffic film. The recognition-memory task consisted of words with intermediate hedonic tone (neutral words), words with high hedonic tone ('good' words) and words with low hedonic tone ('bad' words). Patients performed slower on perceptual-motor tasks which could be characterized as effort-demanding, while no difference between groups was found on effortless tasks. In addition, the range of horizontal eye movements, an indication of visual span, was found to be less in patients. Signal-detection analysis on the recognition-memory data showed an impairment of 'pure' memory in depressives. Analyses on response bias indicated that patients had more false alarms, but only with respect to good words. It is concluded that patients exhibit cognitive deficits, including memory impairment, a narrower visual span and a risky response strategy on good words, which may be an indication of the trouble patients have in processing emotionally toned words.

Birth weight in opposite sex twins as compared to same sex dizygotic twins

The question addressed in the present report is whether the large birth weight differences in dizygotic twin pairs of opposite sex (DZos), especially in 'male first' couples--observed by Blickstein and Weissman (Blickstein I, Weissman A. Birth weight discordancy in male-first and female-first pairs of unlike-sexed twins. Am J Obstet Gynecol 1990;162:661-663) and replicated in the present study--can be explained by two general influences on birth weight, viz. sex and birth order, or whether some specific effect on fetal growth has to be assumed that is present only in twin pairs of differing sex. The associated enhanced health risk would hit the female twin (from a male first-female second couple) in the first place. If the hypothesis is correct, then one may expect that birth weight of twins is somehow dependent on the sex of the co-twin. This was studied in 3069 twin pairs born in The Netherlands since the end of 1986. Results show that among DZ twins, birth weight is not affected by the sex of the co-twin. Therefore, birth weight differences in DZos pairs have to be ascribed to the general effects of sex and birth order. There is no effect that is specific to DZos pairs only.

Epidemiological and birth weight characteristics of triplets: a study from the Dutch twin register

From 112 triplet sets, born in The Netherlands from the end of 1986 to the beginning of 1991 and registered in the Dutch Twin Register, several details such as birth weight, gestational age, zygosity, and etiology were assessed by questionnaire, which was filled out by the mother. For 33 triplet sets, zygosity was also assessed by blood typing. Maternal smoking during pregnancy was also noted. Results show a very strong increase in number of triplets caused by artificial fertility enhancing techniques and consequently a shift in the relative contribution of zygosity types to the total number of triplets. Birth weight is predominantly influenced by gestational age. Other effects on birth weight are controlled for possible confounding with gestational age. First born triplets weigh more than later born triplets; boys weigh more than girls; nearly 25% of all individual triplets weigh less than 1500 g, i.e. belong to the category very low birth weight (VLBW); regular maternal smoking produces a 14% birth weight reduction; ovulation induction seems to decrease the sex ratio, i.e. hormonal treatment with ovulation inducing substances increases the probability of female offspring.

Regular exercise and aerobic fitness in relation to psychological make-up and physiological stress reactivity

This study assessed the association of aerobic fitness with psychological make-up and physiological stress-reactivity in a group of untrained men, as well as the effects of 4 and 8 months of exercise training on these parameters. Psychological assessment included questionnaires on personality (Neuroticism, Type A, Hostility), coping styles (Anger In, Anger Out), negative affect (Depression, Anxiety), and self-esteem. Stress reactivity was measured as the cardiovascular and urinary catecholamine response to two competitive reaction time tasks and the cold pressor test. No cross sectional relationships were found between aerobic fitness, defined as the maximal oxygen consumption during an exhaustive exercise test, and any of the psychological variables. In addition, psychological make-up did not change as a consequence of exercise training. In further contrast to our hypothesis, aerobic fitness was associated with high, rather than low, cardiovascular reactivity. Longitudinal effects of training were limited to a reduction in the overall levels of heart rate and diastolic blood pressure. This suggests that regular exercise does not increase the resistance to stress-related disease by influencing psychological make-up or acute psychophysiologic reactivity.

Abnormal extracranial vasomotor response in migraine sufferers to real-life stress

Temporal and digital pulse amplitudes, forehead temperature, heart rate, respiration rate and electrodermal activity of 37 migraine patients and 37 matched controls from a population of psychology students were recorded during three experimental sessions: adaptation, real-life stress (an examination) and experimental stress (an IQ test). Migraine sufferers showed significantly smaller pulse amplitudes of the temporal artery during the examination than the control group. No group differences were present in the other physiological measures. The findings are interpreted as indirect evidence for the symptom specificity hypothesis, which states that individuals with specific psychosomatic complaints display abnormal responses to stress in the relevant physiological system.

The Dutch Twin Register: growth data on weight and height

As part of a longitudinal developmental study of newborn and young Dutch twins, data on weight and height are collected. Birth weight and height are available for 3275 pairs; data on growth, for 1390 pairs.

Vitamin B-6 supplementation in elderly men: effects on mood, memory, performance and mental effort

This study evaluates the effects of vitamin B-6 supplementation (20 mg pyridoxine HCL daily for 3 months) on mood and performance in 38 self-supporting healthy men, aged between 70-79 years. Effects were compared with 38 controls who received placebo and were matched for age, plasma pyridoxal-5'-phosphate (PLP) concentration and intelligence score. Before and after drug intervention vitamin B-6 status was determined, and mood and performance were measured by means of a computerized testing system. In addition, the phasic pupil response was measured in order to assess mental effort. Positive effects of vitamin B-6 supplementation were only found with respect to memory, especially concerning long-term memory. In view of the finding that mental performance improvement and delta PLP values were most strongly correlated within an intermediate range of delta PLP, it is suggested that cognitive effects are primarily associated with a certain range of vitamin B-6 status increment. The general conclusion is that vitamin B-6 supplementation improves storage of information modestly but significantly.

Changes in the DZ unlike/like sex ratio in The Netherlands

Based on Dutch twin incidence figures since the beginning of the current century, evidence is provided in support of the idea that the DZ unlike/like sexed ratio has gradually shifted (since 1900) from unity to less than unity. Opposing conclusions with regard to the justification of the use of Weingberg's differential rule are very probably correct in themselves but could depend on country and period of birth of the twin sample used. Furthermore, the fast drop and subsequent rise in DZ twinning rate between about 1963 and 1990 can very likely for the greater part be ascribed to a parallel shift in maternal age.

HGM1: a research-oriented portable heart rate and galvanic skin response monitor

A convenient portable recording device, HGM1, which allows digital field recording of skin conductance and heart rate data with laboratory levels of precision, is described. Examples of individual data are provided from a study of orienting response habituation, and from students participating in a study of examination anxiety, recorded while they sat scheduled class examinations. These illustrate the potential value of the device in field studies.

Residual effects of lormetazepam on mood and performance in healthy elderly volunteers

45 subjects aged over 65 years were randomly assigned to treatment with lormetazepam 0.5 mg or 1 mg or placebo. Mood and performance were measured with a battery of computerized tests. Subjects were tested before and after 1 and 8 nights of treatment. Pre- and post-treatment scores were analysed by a multivariate covariance technique, the pre-treatment score serving as covariate. The single and repeated doses of lormetazepam resulted in impairment of performance in a memory task, and the repeated dose administration impaired performance of a perceptual task. The single administration of a low dose gave an improvement in fine motor control. No change was found in the mood states of the subjects.

Relaxation training in school classes does not reduce headache complaints

The effect of teacher-presented Progressive Relaxation Training (PRT) on headaches, fear of failure and school problems was studied in school students. During ten physical education lessons, students received either PRT (n = 110) or placebo training (n = 92). The effect of the training was investigated in students who indicated the presence of headaches in a pre-training diary. No significant differences were found between both training groups regarding headache frequency, duration and intensity and the psychological variables. On the basis of these and previous findings, it is recommended to present PRT to fairly small groups of self-selected subjects instead of complete classes.

Existing and training induced differences in aerobic fitness: their relationship to physiological response patterns during different types of stress

Aerobic fitness has been associated with various desirable psychological and physiological characteristics. Recently, attenuation of physiological reactivity during stressful situations was added to this list, although comparison of the stress responses of sportsmen and sedentary subjects has yielded equivocal results. The present study examined cardiovascular patterns rather than single variables, and tried to clarify these matters. Tasks were used that were known to increase blood pressure through different combinations of changes in cardiac output and vascular resistance. Autonomic nervous system dynamics underlying these response patterns were studied using preejection period as an index of beta-adrenergic activity, and respiratory sinus arrhythmia as an index of vagal activity. Pre-existing differences in aerobic fitness in a sample of sedentary subjects were related to their responses during the stressful tasks and the recovery periods afterwards. This approach prevented confounding of the relationship between fitness and stress-reactivity with the psychological effects of regular exercise. Furthermore, it excluded the bias in psychological makeup that is introduced when subjects spontaneously engaged in sports are compared to non-exercising persons. To rule out a third (hereditary?) factor underlying both stress-reactivity and fitness, physiological responses before and after a seven-week training program were compared to those of subjects in a waiting list control group. Substantial individual differences in aerobic fitness were found in spite of the fact that all subjects reported low levels of habitual activity. During two active coping tasks, diastolic blood pressure reactivity and vagal withdrawal were negatively related to these pre-existing differences in fitness. No such relation was seen during a cold pressor test or during recovery from the tasks. Neither beta-adrenergic cardiac reactivity nor heart rate responses were related to fitness, but the absolute heart rate during the tasks was lower in the more fit subjects. Seven weeks of training were not effective in changing either reactivity or recovery of any of the variables. The discrepancy between cross-sectional and longitudinal results in the present study suggests that training of longer duration is necessary to induce the psychological or physiological changes underlying reduced reactivity. The latter may include changes in cardiac vagal/sympathetic balance or in adrenoceptor sensitivity. Alternatively, both psychological and physiological determinants of stress-reactivity may be related to aerobic fitness at a dispositional level.

Migraine patients cognitively impaired?

In order to investigate the hypothesis that migraine has a detrimental effect on cognitive functioning, 37 female migraine patients and 34 nonheadache female controls underwent a battery of neuropsychologic tests. No significant difference in test performance between groups was found. There was no relation between the length of migraine history or medication use and the level of impairment of cognitive abilities. The patient and control groups differed significantly on several self-report measures known to interfere with performance. Patients reported higher trait and state anxiety levels, higher debilitating anxiety and state depression, and less vigor. Statistical correction for these variables, however, did not result in significant group differences of cognitive performance. The results suggest that the general population of female migraine patients show no indication of cognitive impairment.

Genetic influences on respiratory sinus arrhythmia across different task conditions

Respiratory sinus arrhythmia (RSA) has been shown to be a sensitive index of vagal cardiac control. We studied the genetic and nongenetic influences on individual differences in RSA in a sample of 160 adolescent twins. RSA was measured during rest and across two different tasks. Results show that heritability is task dependent. The amount of genetic variance is the same, however, during rest and task conditions. Because nonshared environmental variance decreases during tasks, heritability is larger for RSA measured under more stressful conditions than for RSA as measured during rest. Multivariate models assessed the continuity of the genetic and environmental influences and show genetic influences to be the same across different conditions, while environmental influences are different. More specifically, a one-factor model is found for genetic influences and a second-order autoregressive model for the environmental factors.

Age migraine and achievement motivation related? A psychophysiological study of responses to real-life achievement stress in young headache sufferers

Achievement motivation and its physiological correlates were studied in 37 young migrainous headache sufferers (30 females and 7 males) and in 37 matched controls. Temporal and digital pulse amplitude, the EMGs of the m. frontalis, anterior temporalis and corrugator supercilii, heart and respiration rate, head temperature and electrodermal activity were measured during an adaptation session, an examination and an intelligence test. An abnormal response in the temporal artery, which was present in the migrainous headache sufferers, was not associated with achievement motivation. But the latter was positively associated with a high skin conductance level, a greater number of spontaneous skin conductance responses (SCRs) during the examination and a lower digital pulse amplitude in both the migrainous headache and control groups. Higher sympathetic activity in subjects with high achievement motivation was interpreted as an indication of greater mental effort and is a possible contributory factor to an attack in those with migraine.

Estimation of individual genetic and environmental factor scores

Implicit in the application of the common-factor model as a method for decomposing trait covariance into a genetic and environmental part is the use of factor scores. In multivariate analyses, it is possible to estimate these factor scores for the communal part of the model. Estimation of scores on latent factors in terms of individual observations within the context of a twin/family study amounts to estimation of individual genetic and environmental scores. Such estimates may be of both theoretical and practical interest and may be provided with confidence intervals around the individual estimates. The method is first illustrated with stimulated twin data and next is applied to blood pressure data obtained in a Dutch sample of 59 male adolescent twin pairs. Subjects with high blood pressure can be distinguished into groups with high genetic or high environmental scores.

Effects of behaviour therapy on migraine and plasma beta-endorphin in young migraine patients

In this study we measured concentrations of beta-endorphin, ACTH, prolactin and cortisol in plasma of migraine patients (ages 10-19) and age-matched controls, and the effects of behaviour therapy on both migraine and the endocrine parameters. Two groups of migraine patients (M) and controls (C) were recruited: group I (MI, n = 11; CI, n = 13) in winter and group II (MII, n = 9; CII, n = 7) in summer. Both M groups received behaviour therapy: group MI immediately and group MII after a waiting period of 3.5 months. Hormone determinations were made before and after the behaviour therapy of group MI and before and after the waiting period of group MII. At the first measurement (before therapy and waiting period), migraine subjects had lower concentrations of beta-endorphin than controls. After behaviour therapy, both groups showed a significant decline in migraine, which was retained at follow-up 9-12 months after completion of the therapy. Improvement of migraine after behaviour therapy was accompanied by a rise in the level of beta-endorphin in group MI. In contrast, the patients of the waiting period (group MII) showed improvement in migraine after the waiting period but no changes in beta-endorphin. Seasonal differences were observed for beta-endorphin, prolactin and cortisol, winter values being lower than summer values.

Comparison of spot and band impedance cardiogram electrodes across different tasks

Impedance cardiography has become of widespread interest as a noninvasive cardiovascular monitoring technique. This study compared the use of spot electrodes and two different types of band electrodes in the determination of systolic time intervals and stroke volume. EKG, impedance cardiogram, and phonocardiogram were recorded on 12 volunteers during rest, during a reaction time task, and after a short exercise task. Systolic time intervals (pre-ejection period and left ventricular ejection time) were computed on a beat-to-beat basis and on the ensemble-averaged signals. The only differences between spot and band electrodes were for impedance base level and electrode conductance. For stroke volume and the systolic time interval measures there were no differences between electrode arrays, nor were there any interactions with tasks. Correlations for stroke volume and systolic time interval measures as determined under different electrode conditions were around .8.

Auditive and cognitive factors in speech perception by elderly listeners. I: Development of test battery

This study compares performance of 24 young normal-hearing (aged 18-28 years) and 24 elderly (aged 61-85 years) listeners on auditive (sensitivity, frequency selectivity, and temporal resolution), cognitive (memory performance, processing speed, and divided attention ability), and speech perception tests (at the phoneme, spondee, and sentence level). Its principal aim is to assess whether the tests selected yield meaningful results. The results obtained will be used to reduce the test battery in order to be manageable in a second study on a much larger number of elderly listeners. The relationships between the tests are explored by multivariate statistical methods. The results show that: (a) in young listeners, individual differences in speech perception performance are remarkably small resulting in low correlations between the tests, while in the elderly tests of phoneme, spondee, and sentence perception overlap considerably; (b) speech perception in the elderly seems to be largely determined by hearing loss at the higher frequencies, whereas the effects of other auditive and cognitive factors seem to be relatively small or absent; and (c) performance in the elderly is only partly correlated with age.

Resemblances of parents and twins in sports participation and heart rate

A model to analyze resemblances of twins and parents using LISREL is outlined and applied to sports participation and heart-rate data. Sports participation and heart rate were measured in 44 monozygotic and 46 dizygotic adolescent twin pairs and in their parents. Genetic factors influence variation in both sports behavior and heart rate, while there is no evidence for transmission from parental environment to offspring environment. For sports participation the data support a model in which there is a high positive correlation between environments of spouses and between environments of female twins. This correlation is absent for male twins and negative for opposite sex twins. For heart rate, a positive correlation between environmental influences was observed for all twins; there is no evidence for assortative mating. The proposed model can also handle data sets where parents and twins have been measured on more than one variable. This is illustrated by an application to the observed association of sports participation and heart rate.

Dietary effects on mood and performance

Of 20 young students recruited at a college for nutrition, 10 followed a diet for a period of 3 weeks and 10 were assigned to a control condition. One subject in the control group dropped out. The diet consisted of approximately 70 g protein and 25 g carbohydrate at breakfast and 10 g protein and 100 g carbohydrate at dinner. In between, a protein luncheon was consumed. On the last day of the 3-week period repeated measurements of mood and performance were made, i.e. after breakfast and after dinner. Consequently, the same measurements were made 2 months later to serve as covariates in the analyses to control for base-line differences of the two groups. It was predicted that, in the morning, the performance and the vigour of the diet group would improve whereas, in the evening, performance would become worse and subjects would feel more sleepy. However, the diet group was found to have a higher anger score in the morning (probably due to the unattractive nature of the diet) and a tendency to have a higher fatigue score in the evening compared with the controls. In addition, the diet group performed better in the morning on finger tapping, compared with the control group. With respect to memory scanning, the diet group performed more slowly in the morning in comparison with the control group. From these conflicting results, it was concluded that dietary composition had no effect on mood and behaviour.

Effects of paroxetine and maprotiline on mood, perceptual-motor skills and eye movements in healthy volunteers

Sixteen healthy young volunteers (seven females, nine males) received repeated doses of either 30 mg paroxetine, 100 mg maprotiline or placebo in a double-blind crossover study. Each of the three treatments lasted 1 week separated by 2 weeks of no treatment. Treatment order was counterbalanced. Subjects were tested before each treatment period, and after 1 and 7 days of treatment. Measurements were made of mood, perceptual-motor skills, and eye movements including pupil size when subjects were watching a traffic film.

EMG in common migraine: changes in absolute and proportional EMG levels during real-life stress

The absolute and proportional EMG levels of the frontal, temporal, and corrugator muscles of 37 migraine patients and 37 matched controls were recorded during three experimental sessions: adaptation and real-life and experimental stress, both of long duration. Migraine patients did not show significantly different absolute EMG levels but had higher proportional EMG levels of the corrugator muscle than controls in each session. Migraine patients did not have different facial muscle responses to stress, and the two experimental groups reacted similarly to real-life and experimental stress. No relation was found between muscle activity and reported headache within 24 h after real-life stress. Increased EMG activity due to stress does not seem to be a significant cause of headache in common migraine as defined in this study, but rather a response to pain. Migraine patients with headache during stress showed lower muscle tension than patients without headache.

Migraine and defense mechanisms: psychophysiological relationships in young females

Two psychological defense mechanisms, repression and self aggression, were studied in 23 young female migraine patients who had not been receiving treatment for their complaints and in 23 relatively headache free matched controls. All subjects were psychology students. Each subject was classified as high or low on repression and self aggression using the defense mechanism inventory. During three separate sessions: adaptation, intelligence test and real-life stress (an examination which was part of the psychology curriculum) pulse amplitudes of the temporal and digital arteries, frontal, temporal and corrugator EMGs, forehead temperature, skin conductance, and heart and respiration rate were measured. The migraine patients showed a trend towards more repression of their emotions and significantly more self aggression than the controls. Self aggression appeared to be positively associated with the headache frequency in the migraine group. With regard to the physiological measurements, in both groups repressors showed a modest tendency to enhanced sympathetic activity. Self aggression was not found to be related to any physiological measure of sympathetic activity, but, instead, related to less temporal blood flow. In general, associations were found between psychological defense mechanisms and physiological activity, which is suggestive of the existence of physiological pathways along which emotional inhibition might contribute to an attack of migraine after a stressful situation.

Aerobic fitness and the physiological stress response: a critical evaluation

Aerobically fit persons need less sympathetic activation to perform the same absolute workload than less fit persons. This led to the idea that aerobic fitness might reduce the physiological activation during psychological stress as well. Several experiments showed inconsistent results with regard to this supposed effect of fitness. The comparability of the results is hampered by the differences in operationalization of aerobic fitness and by the confusion of the terms aerobic fitness, training and habitual physical exercise. The expectancy of an effect of fitness on the physiological stress response is based on the assumption that this response resembles the response to exercise. The tenability of this assumption was examined for cardiac, vascular and hormonal responses respectively. It was concluded that the two types of responses only superficially have similarity. So a simple analogy between the stress and the exercise response does not allow a reliable prediction concerning the effect of fitness on the stress response. There are however other reasons to expect an effect. Especially the effect of fitness on adrenoceptor sensitivity suggests that the most important effect of fitness might be found in the vascular part of the stress response. It is argued that the measurement of complete response patterns, instead of isolated parameters, is a prerequisite for progress in this field. Future studies should address the question what the relative contribution of psychological and physiological factors is to the effect of fitness on the physiological stress response.