Platelet MAO and measures of attention and impulsivity in boys with attention deficit disorder and hyperactivity

Platelet monoamine oxidase (MAO) activity was studied in 22 boys diagnosed as having attention deficit disorder with hyperactivity and 12 healthy control boys admitted to a clinical research center and placed on a diet low in monoamines. The hyperactive boys had lower platelet MAO activity than controls, and MAO activity was related to performance on the Matching Familiar Figures Test (MFF) and the Continuous Performance Test (CPT), which yield scores sensitive to impulsivity and inattention. Furthermore, it was negatively related, in hyperactive boys only, to two tests of reading and spelling achievement. Administration of d-amphetamine and placebo in a double-blind crossover design did not significantly raise MAO levels above baseline and was minimally related to improved performance on the MFF and CPT.     

Psychoeducational and impulsivity correlates of platelet MAO in normal children

The authors examined the relationship between the activity of platelet monoamine oxidase (MAO) and a variety of psychoeducational measures, as well as the scores on the Matching Familiar Figures Test (MFF), a psychological test of reflection-impulsivity, in 21 normal children (12 boys, 9 girls) who were admitted to a clinical research center and placed on a low monoamine diet. The children were divided into three equal groups (n = 7) based on their values of platelet MAO. There were no significant differences among the three groups in the psychoeducational measures. However, the high and low MAO groups made significantly more errors and had shorter latency periods on the MFF than the middle MAO group. These findings suggest that normal children with platelet MAO activity values in the high and low ends of the MAO distribution are more impulsive than the children with platelet MAO values in the middle range on the MFF Test of Impulsivity. The findings further suggest that there is no relationship between platelet MAO levels and intellectual abilities or scholastic achievement in normal children.     

DBH, MHPG, and MAO in children with depressive, anxiety, and conduct disorders: relationship to diagnosis and symptom ratings

Plasma 3-methoxy-4-hydroxyphenylglycol (MHPG), plasma dopamine-beta-hydroxylase (DBH) activity, and platelet monoamine oxidase (MAO) were obtained in 42 boys (7-14 years old) consecutively evaluated at a community mental health clinic. The boys were diagnosed according to DSM-III criteria by a child psychiatrist using a semistructured interview with the parent and child. The Revised Behavior Problem Checklist (RBPC) and the Revised Children's Manifest Anxiety Scale (RCMAS) were consecutively obtained on the last 24 subjects. No relationship of any of the plasma measures was found with respect to the DSM-III diagnoses. Plasma MHPG was positively correlated with the parent's rating of the child's anxiety on the Anxiety-Withdrawal factor of the RBPC. Plasma MHPG as well as platelet MAO activity, correlated positively with the child's self-rating of anxiety on the RCMAS. Children classified by the RBPC as having high conduct symptoms and low anxiety symptoms had significantly lower plasma MHPG than those subjects with low conduct problems and high anxiety. Platelet MAO activity was found to be negatively correlated to the child's score on the Lie Scale of the RCMAS.     

Platelet glutathione peroxidase and monoamine oxidase activity in schizophrenics with CT scan abnormalities: relation to psychosocial variables

We have previously reported that the activity in platelets of the important antioxidant enzyme glutathione peroxidase (GPx) is inversely correlated with computed tomographic (CT) measures of brain atrophy in a population of patients with chronic schizophrenia, suggesting that low GPx may be a vulnerability factor in those schizophrenic patients with structural brain abnormalities. The significance of this finding has now been explored in a larger clinical population by examining the relation of GPx and CT parameters to psychosocial variables and to the activity of platelet monoamine oxidase (MAO), which has also been reported to be altered in certain schizophrenic populations. In the present study, low platelet GPx and high brain atrophy were found to be associated with DSM-III diagnoses of nonparanoid schizophrenia, a high degree of chronicity, and a predominance of negative symptoms. Contrary to some literature reports, atrophy also correlated with age and length of illness among the schizophrenic patients, although the contribution of these factors was less than that of low GPx, which was itself not age dependent. The ventricle-brain ratio (VBR) and atrophy were highly correlated in a control group of affective disorder patients, but not in the schizophrenic group, where large VBRs were found predominantly in the DSM-III undifferentiated subgroup. The low-GPx/high-atrophy schizophrenic patients had normal platelet MAO levels, and MAO was significantly lower only in the paranoid subgroup, consistent with reported observations. There was no evidence for a neuroleptic-induced effect on either enzyme.     

Exploring the connections between platelet monoamine oxidase activity and behavior: relationships with performance in neuropsychological tasks

Platelet MAO activity has been found to have behavioral (psychiatric and personality) correlates. The purpose of the present study was to explore the nature of the connections between platelet MAO activity and behavior by analyzing performance in neuropsychological tasks in relation to platelet MAO activity, measured in 37 male subjects. The following neuropsychological tests were given: a finger tapping and alternation test, a reaction time test, a perceptual maze test, a perspective fluctuation task (the Necker cube), and a lexical decision task. The reaction time tasks comprised a motor disinhibition task, in which auditory stimuli given simultaneously with light stimuli were signals for response inhibition. Significant relationships were obtained between low MAO activity and short response times and small variations in response times to left-sided visual stimuli, suggesting a readiness for higher right hemisphere activation in low MAO subjects, and between low platelet MAO activity and many perspective reversals, in line with expectations. Furthermore, high MAO subjects had equal tapping speed for both hands, which has been found in schizophrenic patients. Of special interest in the present results is the strong negative relationship obtained between platelet MAO activity and number of failed inhibitions in the motor disinhibition task, which in a multiple regression analysis highly significantly contributed to the prediction of platelet MAO activity. This finding is in line with the poor passive avoidance performance associated with serotonergic deficiency and syndromes of disinhibition, and thus supports the assumption that platelet MAO activity may be considered as a genetic marker for some properties of the central serotonergic system.     

Platelet MAO activity in anorexia nervosa patients with and without a major depressive disorder

Platelet MAO activity was determined in 33 anorexia nervosa patients. A subgroup of 15 patients who met Research Diagnostic Criteria for a concomitant major depressive disorder were found to have, both initially and after 5 weeks of treatment, significantly lower mean platelet monoamine oxidase (MAO) activity than 28 matched normal control subjects. In contrast, mean platelet MAO activity in the patients who did not meet criteria for major depressive disorder was similar to values in control subjects. The authors found that significantly more depressed patients had low MAO activity compared with nondepressed patients and controls. Platelet MAO activity may be useful in discriminating among subtypes of anorexia nervosa patients.     

Executive cognitive functions and impulsivity as correlates of risk taking and problem behavior in preadolescents

Initiation of drug use and other risky behavior in preadolescence is associated with poor developmental outcomes. In this research, we examine models that ascribe the trajectory to (a) weak executive cognitive function (ECF), (b) early manifestation of externalizing problems, or (c) heightened levels of trait impulsivity. We test the explanatory power of these factors in a structural equation model with a community sample of 387 preadolescents ages 10–12 years. Participants were tested with a computerized battery of tasks to assess three facets of ECF (working memory, cognitive control, and reward processing) as well as with an audio assisted computerized self-interview to obtain reports of impulsivity and risk behaviors (use of cigarettes and alcohol as well as engaging in fighting and gambling for money) and a self-administered questionnaire to assess externalizing and internalizing problems. The best fitting model explained both early risk taking and externalizing symptoms as the result of individual differences in impulsivity. Although no ECF was directly related to risk taking, working memory and one measure of reward processing performance (reversal learning) were inversely related to impulsivity. The results are discussed in regard to theories of early risk taking with particular focus on the potential relation between ECF and impulsive behavior tendencies and the implications for early intervention to prevent the dysfunctional trajectory associated with early risk behavior.     

Impulsivity in overweight children

Objective This study investigates whether or not obese children have a stronger tendency to act on impulse than normal weight children, taking into account the multidimensionality and complexity of the impulsivity construct. Method A performance based test (Matching Familiar Figure Test, MFFT), a child interview and questionnaire, and parental reports were obtained from 56 overweight children and 53 normal weight children aged 10–18 years. Results Overweight children responded in a more impulsive way on the MFFT (P < .01). On the child questionnaire, overweight boys reported more problems with focussing attention (P < .05) and both overweight boys and girls reported being worse at shifting their attention compared with normal weight children (P < .05). In particular, overweight boys showed more impulsivity (P < .05), hyperactivity (P < .01), and inattention symptoms (P < .001) as measured via the clinical interview. Parents of overweight children reported an equal amount of impulsivity and hyperactivity symptoms as parents of normal weight children, but scored their children lower on the Conscientiousness personality dimension (P < .01). Conclusion A subgroup of overweight children appears to have a stronger tendency to act on impulse than normal weight children, and demonstrated an impulsivity prone personality. Hence, overweight children should be screened for impulse control deficiencies. More research is needed to clear out the robustness of gender differences, the existence of a specific personality profile and possibly common underlying mechanisms of childhood obesity and Attention Deficit Hyperactivity Disorder.     

Platelet monoamine oxidase as a function of nongenetic factors

The level of platelet monoamine oxidase (MAO) has been found to be abnormally low in certain types of schizophrenia and in a number of other pathological conditions. It has been suggested that MAO in platelets may be a genetic marker for a subgroup of patients with schizophrenia; however, we have demonstrated that several nongenetic factors influence platelet MAO activity by affecting the platelet rather than the MAO enzyme protein. We have observed platelet MAO activities to be heterogeneously distributed in a given subject's platelet population, heavy platelet fractions having significantly higher specific activity than light platelet fractions. We have also found platelet MAO activity to be significantly correlated with mean platelet volume, platelet protein densities, and protein content per platelet. These changes, which might be induced by drugs and stress, could modify production, mobilization, and clearance of platelets and, hence, influence apparent MAO activity.     

Criminality and platelet monoamine oxidase activity in former juvenile delinquents as adults

Platelet monoamine oxidase (MAO) activity was estimated in 70 former delinquent boys and 40 controls now aged 38–46 years. Platelet MAO activity was compared with their early criminal behaviour (before the age of 15) and their late registered criminality from the age of 15). Mean platelet MAO activity in subjects with both early and late criminality was significantly lower than that in former delinquents without late criminality. There was no significant difference in mean platelet MAO activity between controls and delinquents with early but no late criminality. When delinquents with early criminality were divided into a low and a high MAO group, the relative risk to be registered for late criminality was about 3.1 times higher for the subjects in the low MAO group. Thus, individuals with low platelet MAO activity run an increased risk of continued criminal behaviour.     

Frontal midline theta activity and platelet MAO in human subjects

The distinctive theta rhythm that appears at the frontal midline during the performance of mental tasks has been designated as frontal midline theta (Fm theta). Fm theta shows individual differences and seems to be related to certain personality traits. In several studies, it has been indicated that low platelet monoamine oxidase (MAO) activity is also associated with certain personality traits. In the present study, we found a negative correlation between the appearance of Fm theta and platelet MAO activity. Subjects with marked extroversion show a high amount of Fm theta and low MAO activity. It is therefore suggested that Fm theta, an electrophysiological marker, may be useful in the investigation of monoamine functions in the central nervous system (CNS) by way of platelet MAO activity, a biochemical marker.     

Characterizing impulsivity in mania

Objective: To determine whether specific aspects of impulsivity (response disinhibition, inability to delay gratification, inattention) differ between healthy and bipolar manic subjects, and whether these aspects of impulsivity were associated with each other and severity of affective symptoms. Methods: Performance of 70 bipolar I manic or mixed patients was compared to that of 34 healthy subjects on three tasks specifically designed to study response inhibition, ability to delay gratification, and attention; namely, a stop signal task, a delayed reward task, and a continuous performance task, respectively. Correlations among tasks and with symptom ratings were also performed. Results: Bipolar subjects demonstrated significant deficits on all three tasks as compared to healthy subjects. Performance on the three tasks was largely independent. Task performance was not significantly associated with the severity of affective symptom ratings. However, measures of response inhibition and attention were sensitive to medication effects. Differences in the delayed reward task were independent of medication effects or symptom ratings. During the delayed reward task, although bipolar patients made their choices more slowly than healthy subjects, they were significantly more likely to choose a smaller, but more quickly obtained reward. Moreover, performance on this task was not associated with performance on the other impulsivity measures. Manic patients showed more impulsive responding than mixed patients. Conclusions: Bipolar I manic patients demonstrate deficits on tests of various aspects of impulsivity as compared to healthy subjects. Some of these differences between groups may be mediated by medication effects. Findings suggested that inability to delay gratification (i.e., delayed reward task) was not simply a result of the speed of decision making or inattention, but rather that it reflected differences between bipolar and healthy subjects in the valuation of reward relative to delay.     

Comparison of whole blood serotonin and platelet MAO in children with schizophrenia and major depressive disorder

Whole blood serotonin and platelet monoamine oxidase (MAO) activity in boys with schizophrenia, schizotypal personality disorder, or major depressive disorder was compared with that of boys serving as controls. Boys with schizophrenia and schizotypal personality disorder had significantly higher platelet MAO than boys with major depressive disorder or controls. Boys with major depressive disorder had lower whole blood serotonin than boys with schizophrenia or schizotypal personality disorder.     

Early morning awakening in unipolar depressives with higher levels of platelet MAO activity

Platelet monoamine oxidase (MAO) activity was analyzed in 51 patients with Major Depressive Disorder. The enzyme activity was correlated univariately and multivariately using split-half techniques with affective subdiagnosis, sex, body measures, and a great many depressive symptoms. The results indicate that unipolarly depressed patients with higher levels of platelet MAO activity woke up earlier in the morning than they had before becoming depressed. Waking up early appeared to be one least common denominator behind higher MAO activities and a unipolar subdiagnosis. Earlier reports on univariately significant differences in MAO activity between affective subdiagnoses or between the sexes were not replicated. Positive trend correlations were found between homovanillic acid and 5-hydroxyindoleacetic acid in cerebrospinal fluid and platelet MAO activity. Urinary free cortisol correlated significantly with platelet MAO activity, but only in unipolars.     

Relationship of platelet MAO activity to characteristics of major depressive illness

Sixty-seven patients (greater than or equal to 55 years of age) with major depressive disorder had pretreatment assays of platelet monoamine oxidase (MAO) activity. As in previous studies, women had higher MAO activity than men, and MAO activity was positively correlated with age. Patients with melancholia (DSM-III) had significantly higher MAO activity than those without melancholia. This finding may reflect the higher MAO activity associated with the symptoms of anhedonia and mood autonomy. Anxiety also was correlated with higher MAO activity, as was a positive family history of depression. In addition, postdexamethasone cortisol levels were correlated with platelet MAO activity.     

Impulsivity and internalizing disorders in childhood

Impulsivity has often been related to externalizing disorders, but little is known about how it is related to symptoms of internalizing disorders. This study aims to examine the relationship between impulsivity and depression and anxiety symptoms of depression and anxiety in childhood, and compare it with its relationship with a measure of aggressive behavior, which is present in many externalizing disorders. We administered the Barratt Impulsiveness Scale-11 for children, the Children's Depression Inventory and the Screen for Children's Anxiety Related Emotional Disorders to a case-control sample of 562 children aged between 9 and 13 who were selected from an epidemiological study of anxiety and depression and whose teachers provided information about their proactive and reactive aggression. Impulsivity was related to measures of anxiety, depression and aggressive behavior, and showed higher relationships with measures of internalizing symptoms than with aggression. Motor impulsivity, a component of impulsivity related to inhibition deficits, was the component most related to anxiety and depression. Cognitive impulsivity, on the other hand, was negatively related to anxiety and depression. The relationships between impulsivity and symptoms of internalizing disorders seem to indicate that impulsivity should be taken into account not only in externalizing problems, but also in depression and anxiety in children and adolescents.     

Relationships between social anxiety,depressive symptoms,and antisocial behaviors: Evidence from a prospective study of adolescent boys

Little is understood about generalized and non-generalized social anxiety disorder (SAD) and their associations with co-occurring internalizing and externalizing problems in adolescence. In the present study, we investigated adolescent boys with SAD symptoms and considered depressive symptoms as well as antisocial behaviors when looking for patterns during two developmental time periods; junior high and high school. Participants in the analyses were part of a longitudinal study. No patterns were found linking antisocial problems and non-generalized SAD in either junior high or high school. Furthermore, it was uncommon for youths in the non-generalized SAD subgroup to develop comorbidity over time. The generalized SAD subgroup of boys, however, was likely to develop comorbidity either with depressive symptoms only or with depressive symptoms and antisocial tendencies. Our findings suggest that developmental pathways for SAD subgroups may differ.     

Personality traits and platelet monoamine oxidase activity in a Swedish male criminal population

BACKGROUND: A Swedish male criminal population was grouped into personality disorder subgroups and investigated with regard to personality traits and platelet monoamine oxidase (MAO) activity. The main aim of the study was to examine the possibility of a risk factor combination by having low platelet MAO activity as well as belonging to a certain diagnostic DSM-IV axis I (drug abuse in the present series) and/or II subgroup. METHODS: Personality disorders were grouped into clusters according to the cluster system used in DSM-IV axis II. The prisoners were grouped into five subgroups and each subject completed the Karolinska Scales of Personality self-report questionnaire. The comparison group for the personality data comprised 51 non-criminal males from a longitudinal Swedish project. Platelet MAO activity was assessed for the criminals as well as for a control group including 60 non-criminal healthy male Caucasians. For testing the existence of syndromes, a configuration frequency analysis (CFA) was used. RESULTS: The results showed low scores on the socialisation and high scores on the sensation seeking-related traits impulsiveness and monotony avoidance, and the somatic anxiety-related muscular tension in the criminals with any DSM-IV mental disorder, however most markedly in cluster AB and cluster B subjects. In addition, cluster AB subjects had significantly lower platelet MAO activity than controls. Two significant 'types' were found among the criminals: one was characterised by low platelet MAO activity, cluster B personality diagnosis as well as drug abuse disorder diagnosis; and the other by a pattern of normal platelet MAO activity, no cluster B personality disorder and no drug abuse disorder diagnosis. CONCLUSION: The aggregation of certain risk factors in the same individual has been shown to contribute to the development of criminal behaviour.