Axis I psychiatric diagnoses in adolescents and young adults with 22q11 deletion syndrome

BACKGROUND

22q11.2 deletion syndrome (22q11DS) associates with schizophrenia spectrum disorders (SSDs), autism spectrum disorders (ASDs), and other psychiatric disorders, but co-occurrence of diagnoses are not well described.

METHODS

We evaluated the co-occurrence of SSDs, ASDs and other axis I psychiatric diagnoses in 31 adolescents and adults with 22q11DS, assessing ASDs using either stringent Collaborative Program for Excellence in Autism (ASD-CPEA) criteria, or less stringent DSM-IV criteria alone (ASD-DSM-IV).

RESULTS

Ten (32%) individuals met criteria for an SSD, five (16%) for ASD-CPEA, and five others (16%) for ASD-DSM-IV. Of those with ASD-CPEA, one (20%) met SSD criteria. Of those with ASD-DSM-IV, four (80%) met SSD criteria. Depressive disorders (8 individuals; 26%) and anxiety disorders (7; 23%) sometimes co-occurred with SSDs and ASDs. SSDs, ASDs, and anxiety occurred predominantly among males and depression predominantly among females.

CONCLUSIONS

Individuals with 22q11DS can manifest SSDs in the presence or absence of ASDs and other axis I diagnoses. The results suggest that standard clinical care should include childhood screening for ASDs, and later periodic screening for all axis I diagnoses.

Movement abnormalities and psychotic-like experiences in childhood: markers of developing schizophrenia?

BACKGROUND

Both involuntary dyskinetic movements and psychotic-like experiences (PLEs) are reported to be antecedents of schizophrenia that may reflect dysfunctional dopaminergic activity in the striatum. The present study compared dyskinetic movement abnormalities displayed by children with multiple antecedents of schizophrenia (ASz), including speech and/or motor developmental lags or problems, internalising/externalising problems in the clinical range, and PLEs, with those displayed by children with no antecedents (noASz).

METHOD

The sample included 21 ASz and 31 noASz children, aged 9-12 years old. None had taken psychotropic medication or had relatives with psychosis. The antecedents of schizophrenia were assessed using questionnaires completed by children and caregivers. A trained rater, blind to group status, coded dyskinetic movement abnormalities using a validated tool from videotapes of interviews with the children.

RESULTS

ASz children reported, on average, 'certain experience' of 2.5 PLEs, while noASz children, by definition, reported none. The ASz children, as compared with noASz children, displayed significantly more dyskinetic movement abnormalities in total, and in the facial and the upper-body regions, after controlling for sex and age. Receiver operator characteristics analyses yielded high area under the curve values for the total score (0.94), facial score (0.91) and upper-body score (0.86), indicating that these scores distinguished between the ASz and noASz children with great accuracy.

CONCLUSIONS

Brief questionnaires identified children with multiple antecedents of schizophrenia who displayed significantly more involuntary dyskinetic movement abnormalities than children without antecedents. The presence of PLEs and dyskinesias could reflect early disruption of striatal dopamine circuits.

Sensitivity to stress among the offspring of parents with bipolar disorder: a study of daytime cortisol levels

BACKGROUND

It is well known that the hypothalamic-pituitary-adrenal (HPA) axis is compromised in major depression and bipolar disorder. There is increasing evidence that subtle HPA abnormalities, such as elevated cortisol levels, precede the development of an affective disorder. Interpersonal stress is also associated with the development of affective disorders. The present study sought to determine whether interpersonal chronic and episodic stress moderated the relationship between cortisol levels in the natural environment and risk status, defined as having a parent with bipolar disorder.

METHOD

Sixty-two offspring of parents with bipolar disorder (OBD) and 60 offspring with no family history of affective disorders (OFH-), aged 19.48 years (s.d.=3.38, range 14-28), completed interviews assessing mental disorders and chronic and episodic stress, and provided saliva samples over 3 days.

RESULTS

Regression analyses revealed that the OBD who experienced high interpersonal chronic stress displayed a larger cortisol rise following awakening than the OBD reporting low interpersonal chronic stress. The same relationship was also found for levels of non-interpersonal chronic stress. The OBD who reported experiencing severe interpersonal episodic stress exhibited higher levels of daytime cortisol than the OBD reporting interpersonal episodic stress of mild severity. Importantly, none of the above relationships were detected in the OFH-. Each of the interactions between family history of affective disorders and stress remained after controlling for age, gender and offspring lifetime affective disorders and current non-affective disorders.

CONCLUSIONS

A biological sensitivity to stress may underlie the susceptibility to affective disorders among the OBD.

Prodromal symptoms in adolescents with 22q11.2 deletion syndrome and schizotypal personality disorder

Adolescents with 22q11.2 Deletion Syndrome (22q11.2DS) and Schizotypal Personality Disorder (SPD) are at increased risk for the development of psychosis based, respectively, on genetic or behavioral factors. Thus both groups would be expected to manifest heightened rates of the prodromal signs that typically precede psychosis. Although there are now standardized procedures for assessing prodromal symptoms, there has been little research on the manifestation of these symptoms in 22q11.2DS patients, and no studies of differences in prodromal symptom patterns between genetically and behaviorally defined at-risk groups. In this study, demographically matched groups of 23 SPD, 23 22q11.2DS, and 23 control participants were administered the Structured Interview for Prodromal Syndromes (SIPS). Both risk groups showed elevated positive, negative, disorganized, and general prodromal symptoms, as well as elevations on 10 of the same individual symptom items, relative to the control group. Approximately 60% of individuals in the 22q11.2DS group and 70% of individuals in the SPD group met symptom criteria for a prodromal psychosis syndrome. The 22q11.2DS group scored significantly higher than the SPD group on the "decreased ideational richness" item and showed a trend toward greater motor abnormalities. The results suggest that these two high-risk groups are similar in prodromal symptom presentation, possibly as a result of overlapping causal mechanisms, and that standardized measures of prodromal syndromes like the SIPS can be used to identify 22q11.2DS patients at greatest risk for conversion to psychosis.

Negative affect in offspring of depressed mothers is predicted by infant cortisol levels at 6 months and maternal depression during pregnancy, but not postpartum

This study tests the hypothesis that maternal depression during pregnancy predicts temperament in offspring aged 6 m to 5 y. Previous studies have shown that maternal depression is related to negative affect and that certain temperament factors, such as negative affect and behavioral inhibition, in children predict affective disorders. Here, maternal depression is divided into depression during pregnancy vs. depression postpartum. Maternal depression was determined by the Beck Depression Inventory (BDI) throughout pregnancy and postpartum (prospectively) and by a diagnostic interview (SCID) at 6 months postpartum. The data show that maternal depression during pregnancy, but not postpartum, predicted the ratings of negative affect in the offspring. Importantly, symptoms of depression in the mother (BDI) were used as a control variable in the analyses in order to control for potential bias related to the mother's mood. In addition, cortisol levels in response to a mild stressor at 6 months of age predicted negative affect in infants and toddlers. We conclude that the effects of maternal depression on behavioral problems and vulnerability to mental illness may be mediated by altered temperament and enhanced stress responsiveness.

Developmental changes in cortisol secretion in normal and at-risk youth

Adolescence is associated with an increase in the rate of certain psychiatric symptoms, and it is typically the developmental period when prodromal features of the major psychiatric disorders emerge. This is especially true of schizophrenia, with the majority of patients showing a marked postpubertal rise in schizotypal signs that predates the onset of clinical symptoms in early adulthood. Cross-sectional studies of youth have revealed a positive correlation between age and saliva cortisol level, suggesting a normative maturational increase in activity of the hypothalamic-pituitary-adrenal (HPA) axis. It has been hypothesized that this increase may trigger the expression of symptoms in vulnerable individuals. The present longitudinal study measured cortisol secretion and its relation with symptom development in samples of youth with schizotypal personality disorder (SPD), other personality disorders, or no Axis II disorder. The findings indicate moderate stability in cortisol levels across a 2-year period, with a longitudinal increase in cortisol levels over time. Cortisol levels at the first and second assessments were correlated with the severity of SPD symptoms at follow-up. The results are consistent with the notion that the HPA axis undergoes a postpubertal maturational process that moderates the expression of psychiatric symptoms.

Cognitive functioning, cortisol release, and symptom severity in patients with schizophrenia

BACKGROUND

There is substantial evidence of dysregulation of cortisol secretion, hippocampal abnormalities, and memory deficits in schizophrenia and other psychotic disorders. Research also suggests that cortisol secretion augments dopaminergic activity, which may result in increased symptom expression in this clinical population.

METHODS

We examined the relations among cortisol release, cognitive performance, and psychotic symptomatology. Subjects were 18 adults with schizophrenia or schizoaffective disorder, seven with a nonpsychotic psychiatric disorder, and 15 normal control subjects. Tests of memory and executive function were administered. Cortisol was assayed from multiple saliva samples.

RESULTS

Findings indicated the following: 1) patients with psychotic disorders scored below the comparison groups on the cognitive measures; 2) for the entire sample, cortisol levels were inversely correlated with performance on memory and frontal tasks; and 3) among patients, cortisol levels were positively correlated with ratings of positive, disorganized, and overall symptom severity, but not with negative symptoms.

CONCLUSIONS

The present results suggest that abnormalities in the hypothalamic-pituitary-adrenal axis and hippocampal systems play a role in observed cognitive deficits across populations. Among psychotic patients, elevated cortisol secretion is linked with greater symptom severity.

Executive functions in adolescents with schizotypal personality disorder

Adolescents meeting diagnostic criteria for schizotypal personality disorder (SPD) are presumed to be at risk for developing schizophrenia in adulthood, making them an important group for exploring the developmental trajectory of the disease. Deficits in executive functioning have been documented in schizophrenia patients and adults with SPD. The present study examined executive functions in adolescents with SPD. It was predicted that the SPD group would score below comparison groups (normals and adolescents with other disorders) on measures of executive function, and that those with greater 'negative' signs of SPD would show more pronounced performance deficits. Analyses revealed that the performance of the SPD subjects was impaired relative to the other groups on the modified Wisconsin Card Sorting Test (MCST), but not on the Tower of London or the Controlled Oral Word Association Test. Consistent with prediction, regression analyses indicated that MCST deficits were associated with greater negative signs of SPD, but not positive signs.

Management of diabetes and hyperglycaemia during myocardial infarction: review of the literature

For many years now, research has firmly demonstrated the increased mortality in patients with diabetes following myocardial infarction (MI), a prognosis which has persisted despite major advances in acute coronary care. Research has also shown higher than usual mortality rates in patients without known diabetes presenting with hyperglycaemia during MI. Due to a lack of research evidence, little has been established about how best to manage glycaemic control in these patients during the acute phase of an MI. However, a recent clinical trial has had considerable impact on coronary care practice. It advocates intravenous insulin therapy for all diabetics and patients with hyperglycaemia during acute MI, followed by subcutaneous insulin for three months, regardless of previous treatment. The evidence for mortality benefit is substantial, but the trial has left some questions unanswered. The aim in this literature review is to examine critically the research basis for using insulin during and after MI, and to identify the potential impact of the research on patients and nurses. The author searched the CINAHL and MEDLINE indexes for relevant texts in English from 1975 to 1998, and has recently implemented relevant knowledge from this research into her own work area, a coronary care unit in the north of England.

Motor dysfunction in schizotypal personality disorder

Past research has revealed that schizophrenia is associated with voluntary movement abnormalities, as well as higher rates of involuntary movements. On instrumental motor tasks, patients manifest reduced motor stability, excessive force and more contralateral motor overflow (movement in the non-responding hand). In the present study, an instrumental motor task (manual response forced-choice task) was administered to a group of adults with schizotypal personality disorder (SPD) in order to determine whether they show motor deficits similar to those observed in schizophrenia. As predicted, the schizotypal subjects were excessive and more variable in motor force, compared to healthy controls and other personality-disordered subjects. Additionally, the force and variability of the motor responses were positively correlated with ratings of both positive and negative SPD symptoms. Finally, motor overflow and negative symptoms were associated with higher salivary cortisol levels. The pattern of findings is consistent with previous reports linking motor abnormalities and heightened cortisol with schizotypal personality disorder.

Developmental neuropathology and the precursors of schizophrenia

Changes in the manifestation of vulnerability to schizophrenia across the lifespan may hold important clues about aetiology. They may also illustrate some general principles about the nature of neurodevelopmental processes. Within the framework of a neural diathesis-stress model, we review findings on the precursors of schizophrenia and schizotypal personality disorder. The findings suggest that there are critical developmental periods for the manifestation of dysfunction and that, within certain domains of behaviour, there is a temporal disjunction between the onset of the neuropathology and its expression. It also appears that the diathesis for schizophrenia involves polymorphic behavioural expression, such that it can be manifested in multiple domains - motoric, cognitive and socio-emotional. Taken together, the data on the longitudinal course of schizophrenia indicate that the expression of the diathesis is moderated by central nervous system maturational processes. One putative moderating system, the hypothalamic-pituitary-adrenal (HPA) axis, is discussed, and implications for preventive intervention are explored.

Schizophrenia: a neural diathesis-stress model

There is a substantive literature on the behavioral effects of psychosocial stressors on schizophrenia. More recently, research has been conducted on neurohormonal indicators of stress responsivity, particularly cortisol release resulting from activation of the hypothalamic-pituitary-adrenal (HPA) axis. This article integrates the psychosocial and biological literatures on stress in schizophrenia, and it offers specific hypotheses about the neural mechanisms involved in the effects of stressors on the diathesis. Both the behavioral and biological data indicate that stress worsens symptoms and that the diathesis is associated with a heightened response to stressors. A neural mechanism for these phenomena is suggested by the augmenting effect of the HPA axis on dopamine (DA) synthesis and receptors. Assuming the diathesis for schizophrenia involves an abnormality in DA receptors, it is proposed that the HPA axis acts as a potentiating system by means of its effects on DA. At the same time, DA receptor abnormality and hippocampal damage render the patient hypersensitive to stress. This neural diathesis-stress model is consistent with findings on prenatal factors and brain abnormalities in schizophrenia, and it provides a framework for explaining some key features of the developmental course and clinical presentation.

Neuromotor functioning and behavior problems in children at risk for psychopathology

Previous studies have found that early neuromotor deficits may be a precursor of later psychopathology. The present study examined the relationship between neuromotor dysfunction and behavioral deviance in children characterized by a variety of risk factors (parental schizophrenia, parental psychiatric disorder other than schizophrenia, and parental maltreatment). The sample consisted of 108 children (average age 9.75 years) who were assessed twice, approximately 1 year apart. It was was found that maltreated children had poorer neuromotor functioning and more behavior problems than children who were not maltreated, regardless of parental psychiatric status. The results also indicated that the relationship between neuromotor functioning and problem behaviors varied as a function of parental psychiatric status. These findings suggest that, although the effects of maltreatment are generalized and pervasive, there are distinctive relationships between neuromotor functioning and behavioral deviance depending on the nature of the risk factors a child has been exposed to.

Childhood behavioral characteristics and adult brain morphology in schizophrenia

It is well established that many schizophrenia patients manifest behavioral dysfunction long before the onset of clinical symptoms of illness. Some show signs of motor and socioemotional deficit as early as infancy. The present study examines the relations among childhood neuromotor, affective and behavior characteristics, and the association of these factors with adult brain morphology (MRI) in schizophrenia patients. Data on neuromotor functions and negative affect were obtained from coding of childhood films. Parents of patients provided information about six dimensions of childhood behavior problems. Analyses of data from patients and healthy siblings revealed that childhood neuromotor abnormalities and negative affect were associated with some of the behavioral dimensions. Among the patients, early childhood neuromotor deficits and negative affect were linked with greater ventricular enlargement in adulthood. The ratings of the behavior problem dimensions showed a complex relation with adult brain morphology, suggesting that externalized problems are linked with more abnormalities (smaller brain volume and larger ventricles), whereas internalized problems are associated with less abnormality. The findings are discussed in light of their implications for the developmental origins of brain abnormalities in schizophrenia.

Sex differences in neuropsychological functioning among schizophrenic patients

OBJECTIVE

The view of schizophrenic men as having poorer premorbid development, earlier age at onset, and worse outcome than schizophrenic women predicts greater neuropsychological impairment in the former than the latter. The authors examined in detail neuropsychological functioning in a large group of schizophrenic patients and a healthy comparison group.

METHOD

Neuropsychological functioning in 132 male and 63 female patients with schizophrenia or schizoaffective disorder was extensively studied and compared with that of 99 (40 male, 59 female) healthy individuals.

RESULTS

As expected, the schizophrenic patients as a group were pervasively and significantly more impaired than the comparison group. Within schizophrenia, in contrast to the prediction, women performed significantly more poorly than men in verbal memory, spatial memory, and visual processing. Female schizophrenic patients also had significantly poorer right than left hemisphere performance, whereas male schizophrenic patients had identical scores for right and left hemisphere impairment.

CONCLUSIONS

The findings are consistent with the hypothesis that schizophrenia among women may be partially understood as a right hemisphere dysfunction. Sampling, diagnostic, and epidemiologic factors may have affected the results.

Developmental pathways to schizophrenia: behavioral subtypes

This study examined childhood behavior problems in schizophrenic patients and their healthy siblings. Childhood Behavior Checklist (T. Achenbach, 1991) ratings were obtained from retrospective maternal reports, for 4 age periods: birth to 4 years, 4 to 8 years, 8 to 12 years, and 12 to 16 years. The results indicated that the patients had a variety of childhood behavior problems when compared to their siblings and that the various types of problems differed in their developmental course. Cluster analysis was conducted on the childhood behavior ratings for the schizophrenic patients, and 2 subgroups emerged. Cluster I showed more pronounced behavioral problems than Cluster II, and some of these problems were apparent in early childhood and increased with age. Cluster I also demonstrated greater neuromotor abnormalities in childhood.

Developmental pathways to schizophrenia: behavioral subtypes

This study examined childhood behavior problems in schizophrenic patients and their healthy siblings. Childhood Behavior Checklist (T. Achenbach, 1991) ratings were obtained from retrospective maternal reports, for 4 age periods: birth to 4 years, 4 to 8 years, 8 to 12 years, and 12 to 16 years. The results indicated that the patients had a variety of childhood behavior problems when compared to their siblings and that the various types of problems differed in their developmental course. Cluster analysis was conducted on the childhood behavior ratings for the schizophrenic patients, and 2 subgroups emerged. Cluster I showed more pronounced behavioral problems than Cluster II, and some of these problems were apparent in early childhood and increased with age. Cluster I also demonstrated greater neuromotor abnormalities in childhood.

Childhood behavioral precursors of adult symptom dimensions in schizophrenia

The present investigation tested the hypothesis that childhood behavioral problems are differentially associated with clinical symptoms in adult-onset schizophrenia. Parents of 29 schizophrenic patients completed questionnaires concerning (1) the childhood behaviors of all their offspring from birth through 15 years of age, and (2) the symptomatology of their schizophrenic offspring. The childhood behavior scale was a modified version of Achenbach's Child Behavior Checklist (1991). Scores were derived for six childhood behavior problem factors: Withdrawal, Anxiety/Depression, Social Problems, Thought Problems, Attention Problems, and Aggression/Delinquency. Ratings of symptoms were based on parental versions of Andreasen's Scale for the Assessment of Positive Symptoms (SAPS; 1983) and Scale for the Assessment of Negative Symptoms (SANS; 1981). Symptomatology scores were computed from the SANS and SAPS following Malla et al.'s (1993) and Liddle's (1987b) tri-dimensional concept of schizophrenia: Reality Distortion, Psychomotor Poverty and Cognitive Disorganization. Regression analyses were conducted to examine the relation between childhood behavior and adult symptomatology in the schizophrenic patients. The results indicated that the Psychomotor Poverty and Cognitive Disorganization dimensions in adult patients are positively associated with Withdrawn behavior and inversely associated with Anxious/Depressed characteristics in childhood. The results are discussed in light of the distinction between primary and secondary negative symptoms, and the three dimension concept of schizophrenia.

Childhood emotional expressions, educational attainment, and age at onset of illness in schizophrenia

This study examined the relation between preschizophrenic subjects' facial expressions of emotion in childhood home movies and two criterion variables: educational level (highest grade completed) and age at onset of illness. Earlier research suggest that premorbid affective blunting is associated with an earlier onset of illness and poorer prognosis in schizophrenia. It was, therefore, predicted that lower rates of both positive and negative facial expressions would be associated with lower levels of educational attainment and earlier age at onset of illness. The results indicated that childhood emotional expressions were not associated with educational level but were linked with age at onset. Preschizophrenic subjects who showed lower rates of negative emotion during late childhood/adolescence were younger at illness onset. Findings are discussed in light of previous reports linking affective symptoms with better prognosis in schizophrenia.

Neuromotor precursors of schizophrenia

Previous research suggests that in addition to being a characteristic of schizophrenia, neuromotor dysfunction also predates the onset of the syndrome. The research reported here was intended to examine further the neuromotor development of children with preschizophrenia traits. This study is part of a larger "archival-observational" project that uses childhood home movies to explore the developmental precursors of schizophrenia. Group comparisons revealed a higher rate of neuromotor abnormalities in the preschizophrenia children when compared to their healthy siblings, preaffective disorder subjects, the healthy siblings of patients with affective disorder, and subjects from families with no mental illness. The preschizophrenia subjects also showed poorer motor skills when compared to their healthy siblings and preaffective disorder subjects. When diagnostic group comparisons were made within age spans, the group differences were significant only in the first 2 years of life. Post hoc analyses also revealed that the preschizophrenia subjects' neuromotor abnormalities occurred primarily on the left side of the body. The abnormalities included choreoathetoid movements and posturing of the upper limbs, similar to the motor signs described in earlier reports on diagnosed schizophrenia patients. The findings are discussed in light of their implications for the developmental origins of schizophrenia. Limitations of the study, including problems with sample representativeness and the reliance on observational data, are also discussed.

Developmentally moderated expressions of the neuropathology underlying schizophrenia

A gradually accumulating body of literature suggests that behavioral dysfunction precedes the onset of the schizophrenic syndrome by many years. Thus, a comprehensive neurodevelopmental model of schizophrenia must encompass these early manifestations of dysfunction as well as the postmorbid period. This article draws on previous research findings as well as recently proposed neurodevelopmental models to offer some further hypotheses about the neurodevelopmental process underlying the changing life-course manifestations of the diathesis for schizophrenia. It is proposed that normal maturational events in the central nervous system moderate the behavioral expression of a congenital neuropathology that affects subcortical regions of the brain that are part of multiple neural circuits. Specifically, it is suggested that the diathesis for schizophrenia involves a functional excess of dopamine activity in the basal ganglia that serves to disrupt these circuits. Findings from empirical research suggest a modal developmental trajectory for schizophrenia in which neuromotor dysfunction is most pronounced in early childhood and late in life, whereas florid psychotic symptomatology is most pronounced in late adolescence and early adulthood. The literature on normal central nervous system development suggests that the feedback circuit linking motor cortex with subcortical structures is maximally metabolically activated, relative to other circuits, early and late in the life course. Thus, subcortical dopamine excess may be predominantly expressed in motoric symptoms during these periods. In contrast, late adolescence and early adulthood are marked by low motor cortex metabolic activity relative to other cortical regions, in particular limbic and frontal regions. In addition, hormonal changes appear to result in a maximal activation of the dopamine system during this developmental period. Thus, it is hypothesized that during this period the neural circuitry abnormality will be primarily behaviorally expressed in psychotic symptoms. Some implications of the model for the study of movement abnormalities and psychotic symptoms are discussed.

Childhood precursors of schizophrenia: facial expressions of emotion

OBJECTIVE

This study sought to determine whether affective abnormalities could be detected in home movies of children who later developed schizophrenia.

METHOD

Trained observers coded facial expressions of emotion of 32 schizophrenic patients and 31 of their healthy siblings from home movies made when they were children. All of the patients met the DSM-III criteria for schizophrenia with onset in late adolescence or early adulthood. The sibling comparison subjects had no history of psychiatric illness. Nine emotions and a neutral category were rated.

RESULTS

Analyses revealed significantly lower proportions of joy expressions among the total expressions of the preschizophrenic female subjects than among the same-sex healthy siblings. This difference extended from infancy through adolescence. Among the male subjects, there were inconsistent differences between diagnostic groups in expressions of joy across age levels. However, both the preschizophrenic male subjects and the preschizophrenic female subjects showed greater negative affect than their same-sex comparison groups.

CONCLUSIONS

These findings lend support to the assumption that vulnerability to schizophrenia may be subtly manifested in emotional behavior long before the onset of clinical symptoms.

Sampling biases in studies of gender and schizophrenia

Gender differences in schizophrenia are of great interest to researchers, and some have recently concluded that female patients suffer from a more benign form of the illness. However, the research findings do not support this conclusion consistently, and some reports suggest greater impairment in female patients. In this article, we discuss the potential effects of sampling biases on the findings from studies that compare male and female patients. More specifically, we assume that females do manifest a less severe schizophrenic illness than males, and we propose that sex differences in severity thresholds for voluntary and involuntary treatment are contributing to inconsistencies in the research findings. Some other sources of sampling bias that may influence findings on gender differences are also discussed.