Markers for vulnerability to psychopathology: temperament traits associated with platelet MAO activity

The functional linkage between platelet MAO activity and psychopathology was explored by analyzing temperamental correlates in 40 male subjects by means of scales from the Eysenck Personality Questionnaire (EPQ), the Zuckerman Sensation Seeking Inventory, and the Karolinska Scales of Personality (KSP). Linear correlations were found with two sensation seeking scales, replicating earlier findings. However, nonlinear correlations predominated. Subjects with intermediate platelet MAO activity had higher scores in conformity scales and lower scores in anxiety and hostility scales than low and high MAO subgroups. Low MAO subjects showed a pattern of higher scores in KSP Impulsiveness, EPQ Neuroticism, and KSP Somatic Anxiety and Irritability and lower scores in KSP Socialization, in line with personality profiles found in alcoholics, psychopaths, and suicide attempters who also tend to have low platelet MAO activity. High MAO subjects scored lower in sensation seeking and conformity scales and higher in KSP Psychasthenia, Muscular Tension and Suspicion scales, consistent with clinical links between high platelet MAO activity and anxiety and paranoia.     

Low platelet monoamine oxidase and sensation seeking in males: an established relationship?

A significant negative correlation between platelet monoamine oxidase (MAO) activity, a stable peripheral enzyme measure under genetic control, and sensation seeking, as measured using the Zuckerman Sensation Seeking Scale (SSS), has been reported for male subjects in several studies. As tobacco smoking has been related to both these measures, in the present study correlations were calculated among smoking and non-smoking male university students. Platelet MAO activity was negatively correlated with the Disinhibition and Total scales of the SSS. These correlations were not significantly different in smokers and non-smokers. The results are discussed in terms of recent evidence of reduced platelet MAO activity in psychiatric patients.     

Platelet monoamine oxidase activity and evoked response as predictors of anxiety and depression derived from the content analysis of speech

Platelet MAO activity has been reported by several investigators to differentiate schizophrenia, schizophrenia related depressive disorders, alcoholism, unipolar and bipolar depression from normal controls. Evoked potentials likewise have differentiated schizophrenic and affective patients. However, the precise relationship between MAO activity, evoked potentials (EP), and psychiatric illness has not been clarified. A possible association between psychopathology and high MAO activity/EP reducing and low MAO activity/EP augmenting has been reported. Such a bidirectionality further confounds results. This study was undertaken to determine the association of psychopathological dimensions found in a group of subjects whose platelet MAO activity and evoked responses were obtained two years earlier. Utilizing the Gottschalk-Gleser verbal behavior scales of Anxiety, Depression, Social Alienation-Personal Disorganization and Cognitive Impairment a significant correlation was revealed between low platelet MAO activity and high Total Anxiety scale and Shame Anxiety subscale scores. Additionally, a significant correlation was demonstrated between reducing evoked potentials and elevated Death Anxiety, Somatic Concerns, and Total Death and Mutilation Depression subscales scores, combined and separately. Furthermore, a significant positive correlation was found between augmenting evoked potentials and Overt Hostility Outward scores. No significant correlations were demonstrated between platelet MAO activity or evoked potentials and Social Alienation-Personal Disorganization or Cognitive Impairment scores. These findings lend support to the position that biological markers may predict predispositions to anxiety and depression.     

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.     

Paranoia and platelet MAO in normals and nonschizophrenic psychiatric groups.

The authors compared the correlation between platelet monoamine oxidase (MAO) activity and the Paranoia (Pa) scale of the Minnesota Multiphasic Personality Inventory in several groups. The data suggest that there is a positive association between high MAO activity and high scores on the Pa scale but only in samples with psychopathology.     

Correlation of platelet MAO activity with introversion: A study on a German rural population

Platelet monoamine oxidase (MAO) activity and personality characteristics were correlated in a sample of 52 men (37 ± SD 13 years) and 54 women (37 ± SD 15 years) from a rural community. Personality characteristics were measured by using the Freiburger Persönlichkeitsinventar (FPI-A). In the males, weak but significant linear correlations (Pearson product-moment and Spearman rank correlations) were found between platelet MAO activity (p-tyramine and benzylamine as substrates) and the extraversion/introversion dimension. In the females, however, there were no consistent significant correlations between MAO activity and FPI test scores. Comparing the top and bottom 25% of the platelet MAO distribution resulted in a significant difference for the second order factor extraversion in the group of men but not in the group of women. The significant correlation between MAO and introversion could not be attributed to cigarette smoking, food consumption, alcohol, or drugs. In accord with previous biochemical-behavior research, it is suggested that reduced platelet MAO activity may, to some extent, reflect an impulsive personality type.     

Psychopathy,platelet MAO activity and criminality among former juvenile delinquents

Psychopathy-related personality traits as well as platelet monoamine oxidase (MAO) activity and criminality from the age of 15 years were studied in a group of 68 male former juvenile delinquents and 32 control subjects. The former juvenile delinquents registered for crime as adults were found to have higher Psychopathy Check List (PCL) scores and lower platelet MA0 activity than either juvenile delinquents who were not registered criminals from the age of 15 years or non-criminal controls. Although PCL scores and platelet MAO activity were unrelated, a configural frequency analysis showed a significant interaction. Individuals with PCL scores, low platelet MAO activity and persistent criminal behaviour constituted a significant ‘type’. Among the 27 former juvenile delinquents who developed persistent criminality, 21 subjects (78%) had PCL scores greater than 0 and low platelet MAO activity, while none of these persistent criminals were characterized by a combination of zero PCL score and high platelet MAO activity.     

Psychological characteristics corresponding to low versus high platelet monoamine oxidase activity.

From an original sample of 375 college students and employees studied for platelet MAO activity, 66 subjects representing the lower and upper deciles of the sample were contacted for further study, including administration of the booklet form of the MMPI. We analyzed what psychological characteristics might be associated with differences in MAO activity and attempted to cross-validate these characteristics by using them to predict the separability of low vs. high MAO subjects. Each subject was randomly assigned to one of two groups in which the low and high MAO subjects were balanced for sex. For 16 women in group A, a MAO scale discriminated low and high subjects with 100% accuracy. For 18 men in group A, a separate MAO scale discriminated with 94% accuracy. To cross-validate these results, the two scales were applied to another population; both discriminated low and high MAO women and men with a combined 97% accuracy. The thematic content of the two scales is discussed in the light of other reports on the psychological characteristics of low and high MAO subjects, including the apparent relationship between the scale content and the clinical features of bipolar affective disorder.     

Type A personalities tend to have low platelet monoamine oxidase activity

This study investigated whether there are relations between type A behaviours and the activity of monoamine oxidase (MAO) in blood platelets. Forty male nonsmokers completed the Jenkins Activity Survey (JAS) and had a blood sample drawn while at work. The JAS was scored in the traditional manner, yielding scores for ambitiousness (factor A), impatience (factor S), competitiveness (factor H) and job involvement (factor J). High scores on JAS scales were associated with low MAO activity in blood platelets; the correlation between platelet MAO activity and job involvement was significant. The findings agree with previous reports in showing relationships between MAO activity and certain personality traits and support the notion that low activity of MAO may contribute to sympathetic hyperreactivity in type A individuals.     

Relationships between attempted suicide, temperamental vulnerability, and violent criminality in a Swedish forensic psychiatric population.

The relationship between suicide attempts and different vulnerability factors was investigated in 61 male subjects during forensic psychiatric examination. Personality traits and psychopathy were determined by means of the Karolinska Scales of Personality (KSP) and the Psychopathy Checklist-Revised (PCL-R). Clinical diagnoses were determined by the use of Structured Clinical Interview for DSM-III-R (SCID). Platelet monoamine oxidase (MAO) activity was investigated in 58 subjects.Suicide attempters had extremely low socialization and high impulsive aggression. This was independent of a history of repeatedly criminal violence or not. They had higher PCL-R scores and lower levels of platelet MAO activity than non-attempters. No relationship was found between suicide attempts and repeated violent criminality. However, among the subjects with repeated criminal violence there was a highly significant difference between suicide attempters and non-attempters, indicating different personality profiles in violent offenders with and without suicidal behavior. Suicidal behavior was significantly associated with borderline personality disorder, but not with any other single DSM-III-R disorder. The results show a far more severe personality disturbance in suicide attempters than in other violent patients in this type of population. Suicidal behavior should therefore be evaluated and treated per se.     

Thrombocyte monoamine oxidase activity and personality traits in women with severe premenstrual syndrome

Women with premenstrual syndrome (PMS) of such severity that they actively had sought medical attention for their symptoms were compared with healthy female students with regard to platelet MAO activity and temperamental correlates by means of the Karolinska Scales of Personality (KSP), scales from the Eysenck Personality Questionnaire (EPQ) and Eysenck's IVE inventory. The women with PMS were divided into two groups; irritability and depression as predominating symptom. No variation in platelet MAO was found during the menstrual cycle, either in patients or in controls. Both PMS groups had significantly lower platelet MAO activity than the controls. There was no difference between the two groups with PMS. Also with regard to personality traits there were considerable differences between the females with PMS and the controls. There were few differences between the two groups of PMS patients. Thus, the patients scored significantly higher as regards somatic anxiety, muscular tension, indirect aggression, verbal aggression and neuroticism and lower as regards socialization than the controls.     

Self-rated aggression related to serum testosterone and platelet MAO activity in female patients with the fibromyalgia syndrome.

To investigate self-rated aggression in relation to platelet MAO activity and serum testosterone in patients with fibromyalgia syndrome (FMS), we administered the Aggression Questionnaire - Revised Swedish Version (AQ-RSV) to 30 female patients with FMS. After correction for age, significant positive correlations were seen between serum testosterone concentrations and the AQ-RSV scores for Verbal Aggression (r=0.36, p<0.05) and Anger (r=0.37, p<0.05), whereas the platelet MAO activity was negatively correlated with the score for Verbal Aggression (r=-0.44, p<0.05). Our results suggest that aggression and irritability in female FMS patients might be increased by elevated testosterone concentrations in combination with reduced capacity of the serotonergic system as reflected by low platelet MAO activity.     

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.     

Low platelet monoamine oxidase activity in pathological gambling

Decreased platelet monoamine oxidase (MAO) activity has been reported in association with sensation-seeking personality type and in some mental disorders associated with a lack of impulse control. Pathological gambling itself has been related with both sensation-seeking and reduced impulse control. Platelet MAO activity was investigated in 15 DSM-III-R pathological gamblers from our outpatient clinic. Gamblers had a significantly lower platelet MAO activity than a group of 25 healthy controls. The range of MAO levels in gamblers was also significantly shorter than in controls. In controls, platelet MAO levels showed the previously described negative correlations with sensation-seeking scores but not in gamblers. The findings are consistent with previous studies showing an association of low platelet MAO activity with impulse control disorders and raise some interesting therapeutic alternatives for pathological gambling.     

Morbidity risk for psychiatric disorders in families of probands with affective disorders divided according to levels of platelet MAO activity

In a series comprising 166 subjects with affective disorders, the lowest and highest quartiles in the male and female platelet monoamine oxidase (MAO) distribution, respectively, were included. The morbidity risk in the first-degree relatives (parents and siblings) of these low and high platelet MAO subjects was determined. First-degree relatives of low platelet MAO probands were found to have an increased morbidity risk for neurotic-reactive depressions and for alcoholism. The results seem to be in line with the biological high-risk paradigm, indicating that platelet MAO could be a biological marker for increased vulnerability. First-degree relatives of high platelet MAO probands were found to have an increased morbidity risk for bipolar affective disorders.     

Platelet monoamine oxidase activity and trace acid levels in plasma of agoraphobic patients

ABSTRACT - Platelet monoamine oxidase activity and plasma trace acid levels in 29 patients classified as agoraphobics was estimated. MAO activity towards p-tyramine and β-phenylethylamine was found to be significantly higher in agoraphobics than in non-agoraphobic depressed patients and healthy controls. In addition plasma p-hydroxyphenylacetic acid levels were low in both agoraphobic and depressed patient groups. All patients were also assessed by Spielberger State Anxiety and the short form of the Beck Depression Inventory scales. No significant correlations could be found between platelet MAO activity or plasma trace acid levels and the psychological scores.     

Platelet monoamine oxidase: low activity in cigarette smokers

Platelet monoamine oxidase (MAO) activity and plasma thiocyanate concentration (an index of smoking behavior) were measured in 109 normal male and female volunteers. MAO activity was significantly lower and plasma thiocyanate concentration significantly higher in smoking volunteers than in nonsmoking volunteers. A significant negative correlation between MAO activity and thiocyanate concentration was observed in female smokers (rs = 0.43, n = 36) but not for male smokers (rs = 0.02, n = 31). In nine smokers who gave up smoking, mean (+/- SD) platelet MAO activity increased significantly (17.5 +/- 4.1 nmole/mg/hour to 24.6 +/- 4.2 nmole/mg/hour). At the same time, mean (+/- SD) plasma thiocyanate concentrations decreased significantly (144 +/- 41 microM to 50 +/- 12 microM). These data suggest that smoking directly or indirectly reduced platelet MAO activity.     

Decreased platelet monoamine oxidase activity in female anorexia nervosa

OBJECTIVE: To study if platelet MAO activity, previously described as a serotonergic index, is modified in a sample of pure restrictive anorectic patients. METHOD: Twenty-five female patients with DSM-IV anorexia nervosa restricting type were studied and compared with 30 healthy female controls. Platelet MAO activity was measured by isotopic methods using C-14 benzylamine. Impulsive personality features were measured with specific rating scales and temperament studied with Cloninger's TCI. RESULTS: Platelet MAO activity was significantly lower (4.3+2.7 nmol/h/ 108 platelets) in the anorectic patients than in the control group (6.7+2.8) (P<0.01). Platelet MAO was inversely correlated with scores on impulsivity scales and positively correlated with the dimension 'persistence' of Cloninger's TCI. CONCLUSION: Platelet MAO activity is lowered in a group of patients with anorexia nervosa and might involve some dysfunction in the regulation of impulse control.     

Are gender differences genetically related to catecholamine metabolism in schizophrenia?

Serum homovanillic acid (HVA) and norepinephrine (NE), serum dopamine-β-hydroxylase (DBH), platelet monoamine oxidase (MAO), and erythrocyte catechol-O-methyltransferase (COMT) have been measured in 86 healthy parents of schizophrenic patients and 36 normal control subjects. The t-test showed that serum HVA concentration was significantly higher in mothers of female patients than in mothers of male patients (p < .05); Kruskal-Wallis analysis revealed a significant difference in erythrocyte COMT activity among the mothers of male patients, mothers of female patients and female control subjects (H = 8.7, df = 2, p < .02); and the Mann-Whitney test demonstrated that erythrocyte COMT activity was significantly increased in mothers of male patients as compared with female control subjects (p < .01), but there were no significant differences in the HVA concentration and COMT activity between the fathers of male and female patients, and male control subjects. There were no significant changes in serum NE concentration, serum DBH and platelet MAO activity in these subjects. The present study suggests that catecholamine metabolism in mothers of schizophrenic patients may play a genetic role in the gender differences of schizophrenia.