Age associations with neural processing of reward anticipation in adolescents with bipolar disorders

How to study psychological mechanisms of mania? A systematic review on the methodology of experimental studies on manic mood dysregulation of leading theories on bipolar disorder

INTRODUCTION

Although there are several psychological theories on bipolar disorders (BD), the empirical evidence on these theories through experimental studies is still limited. The current study systematically reviews experimental methods used in studies on the main theories of BD: Reward Hypersensitivity Theory (RST) or Behavioral Activation System (BAS), Integrative Cognitive Model (ICM), Positive Emotion Persistence (PEP), Manic Defense theory (MD), and Mental Imagery (MI). The primary aim is to provide an overview of the used methods and to identify limitations and suggest areas of improvement.

METHODS

A systematic search of six databases until October 2023 was conducted. Study selection involved two independent reviewers extracting data on experimental study design and methodology.

RESULTS

A total of 84 experimental studies were reviewed. BAS and RST were the most frequently studied theories. The majority of these experimental studies focus on mechanisms of reward sensitivity. Other important elements of the reviewed theories, such as goal setting and-attainment, situation selection (avoidance or approach), activation, affective/emotional reactivity, and regulatory strategies, are understudied. Self-report and neuropsychological tasks are most often used, while mood induction and physiological measures are rarely used.

CONCLUSION

There is a need for more consensus on the operationalization of psychological theories of mania. Standardization of test batteries could improve comparability among studies and foster a more systematic approach to experimental research. Research on affective (activated) states is still underrepresented in comparison with studies on trait vulnerabilities.

Misperceiving Momentum: Computational Mechanisms of Biased Striatal Reward Prediction Errors in Bipolar Disorder

Background

Dysregulated reward processing and mood instability are core features of bipolar disorder that have largely been considered separately, with contradictory findings. We sought to test a mechanistic account that emphasizes an excessive tendency in bipolar disorder to enter recursive cycles in which reward perception is biased by signals that the environment may be changing for the better or worse.

Methods

Participants completed a probabilistic reward task with functional magnetic resonance imaging. Using an influential computational model, we ascertained whether participants with bipolar disorder (n = 21) showed greater striatal tracking of momentum-biased reward prediction errors (RPEs) than matched control participants (n = 21). We conducted psychophysiological interaction analyses to quantify the degree to which each group modulated functional connectivity between the ventral striatum and left anterior insula in response to fluctuations in momentum.

Results

In participants with bipolar disorder, but not control participants, the momentum-biased RPE model accounted for significant additional variance in striatal activity beyond a standard model of veridical RPEs. Compared with control participants, participants with bipolar disorder exhibited lower insular-striatal functional connectivity modulated by momentum-biased RPEs, an effect that was more pronounced as a function of current manic symptoms.

Conclusions

Consistent with existing theory, we found evidence that bipolar disorder is associated with a tendency for momentum to excessively bias striatal tracking of RPEs. We identified impaired insular-striatal connectivity as a possible locus for this propensity. We argue that computational psychiatric approaches that examine momentary shifts in reward and mood dynamics have strong potential for yielding new mechanistic insights and intervention targets.

Neural abnormalities of reward processing in adolescents with bipolar disorders: An ERP study

Adolescent onset is common in bipolar disorders (BDs) and is associated with a worse illness course in adulthood. A model of BDs suggests that a dysregulated behavioral approach system (BAS), a neural system that mobilizes reward-seeking behavior, is at the root of BDs. Normative adolescence is often accompanied by dynamic changes to neural structures underlying the BAS and related cognitive processes. It is possible that adolescent-onset BDs is associated with abnormal BAS neurodevelopment. Consistently, the present study is the first to compare specific BAS-relevant anticipatory and consummatory reward processes as indexed by event-related potentials (ERPs) in adolescents with BDs and typically developing peers. Using a sample of 43 adolescents with BDs and 56 without psychopathology, we analyzed N1 and P3 responses to anticipatory cues and feedback-related negativity (FRN) and P3 responses to feedback stimuli during a monetary incentive delay (MID) task. Hierarchical linear models examined relationships between ERP amplitudes and diagnostic group, MID condition, sex, and age. During anticipation phase, adolescent boys with BDs exhibited significantly larger N1 amplitudes in loss than even or gain trials. During feedback phase, compared to their healthy peers, adolescents with BDs had smaller FRN amplitudes across all conditions. Additional effects involving age, sex and trial type were observed. The findings indicate subtle, non-ubiquitous BAS-relevant neural abnormalities involving early attentional processes during reward anticipation and reward learning following feedback in adolescents with BDs. Adolescents with BDs did not show overall hypersensitive neural responses to monetary reward anticipation or feedback observed in adults with BDs.

Mood Symptom Dimensions and Developmental Differences in Neurocognition in Adolescence

Adolescence is critical period of neurocognitive development as well as increased prevalence of mood pathology. This cross-sectional study replicated developmental patterns of neurocognition and tested whether mood symptoms moderated developmental effects. Participants were 419 adolescents (n=246 with current mood disorders) who completed reward learning and executive functioning tasks, and reported on age, puberty, and mood symptoms. Structural equation modeling revealed a quadratic relationship between puberty and reward learning performance that was moderated by symptom severity: in early puberty, adolescents reporting higher manic symptoms exhibited heightened reward learning performance (better maximizing of rewards on learning tasks), whereas adolescents reporting elevated anhedonia showed blunted reward learning performance. Models also showed a linear relationship between age and executive functioning that was moderated by manic symptoms: adolescents reporting higher mania showed poorer executive functioning at older ages. Findings suggest neurocognitive development is altered in adolescents with mood pathology and suggest directions for longitudinal studies.

Peculiarities of personality adaption to psychological traumas in neurotic disorders

BACKGROUND AND AIM

It is known that anticipatory processes play a leading role in the regulation of behavior. These processes act as a leading mechanism of the link in the mental regulation of behavior and activity. Violation of processes anticipates to a mismatch in the work of the adaption system, and, as a result, to maladaptive behavior. However, many issues related to the detection of anticipation disorders in various manifestations of diseases have been insufficiently studied. The features of individual prognosis depending on diseases are studied here.

MATERIALS AND METHODS

As part of the work, 29 people were examined, of which 25 (86.2%) were women and 4 (13.8%) were men with a diagnosis of "adaptive reaction disorder" from the ICD-10 section "Neurotic and stress-related disorders" (F43.2) at the age of 20-65 years. Clinical-psychopathological and experimental-psychological research methods were applied (V.D. Mendelevich's test of anticipation, L.A. Regush's "Ability to predict" test, Lazarus' coping test, clinical questionnaire for the identification and evaluation of neurotic states). Statistical analysis was carried out using the program "IBM SPSS Statistics 25." The Shapiro-Wilk criterion, Pearson's chi-squared test, Fisher's exact criterion, Student's t-criterion, Mann-Whitney U criterion, Kruskal-Wallis H criterion, Pearson correlation, Spearman's correlation, and diagrams (columnar and span) were used.

RESULTS

The presence of solvency in general anticipation reduced the severity of coping strategies «distancing» (P = 0.048, r = -0.371) and «escape - avoiding» (P = 0.048, r = -0.370), also personal-situational anticipatory consistency reduced severity of «escape - avoiding» (P = 0.017, r = -0.438).

CONCLUSION

The anticipatory abilities and coping strategies in disorder of adaptive reactions were correlated. Patients with developed anticipation abilities are less likely to use no constructive coping strategies.

Neural correlates of reward processing distinguish healthy youth at familial risk for bipolar disorder from youth at familial risk for major depressive disorder

Youth at familial risk for bipolar disorder (BD-risk) and major depressive disorder (MDD-risk) have aberrant reward processing, a core feature of these mood disorders. Whether BD risk differentiates from MDD risk in reward processing merits further study. We compared neural activation and connectivity during anticipation and outcome of monetary gain and loss during fMRI using the Monetary Incentive Delay (MID) Task among BD-risk (n = 40), MDD-risk (n = 41), and healthy comparison youth (HC) (n = 45), in the absence of any lifetime or current history of psychopathology [mean age 13.09 ± 2.58, 56.3% female]. Participants completed the MID task at baseline and were followed for behavioral and clinical outcomes over 4.37 ± 2.29 years. Region-of-interest (ROI) analyses conducted using anatomically defined thalamus, ventrolateral prefrontal cortex, nucleus accumbens, and putamen seeds showed that relative to MDD-risk and HC, BD-risk had decreased activation of the thalamus during anticipation of monetary gain [F(2,118) = 4.64, p = 0.01 (FDR-corrected p = 0.04)]. Psychophysiological interaction analyses revealed that BD-risk had less connectivity between the thalamus and left middle frontal gyrus (Z > 3.1, p < 0.001) and left-superior temporal gyrus (Z > 3.1, p < 0.05) compared with MDD-risk. Voxelwise, BD-risk had decreased activation in the cerebellum during anticipation and outcome of monetary gain relative to MDD-risk and HC (Z > 3.1, p < 0.001; Z > 3.1, p < 0.01). In BD-risk, decreased thalamic connectivity was associated with increased impulsivity at baseline and reduced prosocial behavior at follow-up. Reduced thalamic activation and connectivity during reward processing may distinguish familial risk for BD from familial risk for MDD and represent early markers of vulnerability that may herald social dysfunction later in adolescence.

Interactions between methodological and interindividual variability: How Monetary Incentive Delay (MID) task contrast maps vary and impact associations with behavior

INTRODUCTION

Phenomena related to reward responsiveness have been extensively studied in their associations with substance use and socioemotional functioning. One important task in this literature is the Monetary Incentive Delay (MID) task. By cueing and delivering performance-contingent reward, the MID task has been demonstrated to elicit robust activation of neural circuits involved in different phases of reward responsiveness. However, systematic evaluations of common MID task contrasts have been limited to between-study comparisons of group-level activation maps, limiting their ability to directly evaluate how researchers' choice of contrasts impacts conclusions about individual differences in reward responsiveness or brain-behavior associations.

METHODS

In a sample of 104 participants (Age Mean = 19.3, SD = 1.3), we evaluate similarities and differences between contrasts in: group- and individual-level activation maps using Jaccard's similarity index, region of interest (ROI) mean signal intensities using Pearson's r, and associations between ROI mean signal intensity and psychological measures using Bayesian correlation.

RESULTS

Our findings demonstrate more similarities than differences between win and loss cues during the anticipation contrast, dissimilarity between some win anticipation contrasts, an apparent deactivation effect in the outcome phase, likely stemming from the blood oxygen level-dependent undershoot, and behavioral associations that are less robust than previously reported.

CONCLUSION

Consistent with recent empirical findings, this work has practical implications for helping researchers interpret prior MID studies and make more informed a priori decisions about how their contrast choices may modify results.

Schizophrenia and bipolar disorder are associated with opposite brain reward anticipation-associated response

Blunted and exaggerated neuronal response to rewards are hypothesized to be core features of schizophrenia spectrum disorders (SZ) and bipolar disorder (BD), respectively. Nonetheless, direct tests of this hypothesis, in which response between SZ and BD is compared in the same study, are lacking. Here we examined the functional correlates of reward processing during the Incentivized Control Engagement Task (ICE-T) using 3T fMRI. Reward-associated activation was examined in 49 healthy controls (HCs), 52 recent-onset individuals with SZ, and 22 recent-onset individuals with Type I BD using anterior cingulate (ACC), anterior insula, and ventral striatal regions of interest. Significant group X reward condition (neutral vs. reward) interactions were observed during reward anticipation in the dorsal ACC (F(2,120) = 4.21, P = 0.017) and right insula (F(2,120) = 4.77, P = 0.010). The ACC interaction was driven by relatively higher activation in the BD group vs. HCs (P = 0.007) and vs. individuals with SZ (P = 0.010). The insula interaction was driven by reduced activation in the SZ group relative to HCs (P = 0.018) and vs. people with BD (P = 0.008). A composite of reward anticipation-associated response across all associated ROIs also differed significantly by diagnosis (F(1,120) = 5.59, P = 0.02), BD > HC > SZ. No effects of group or group X reward interactions were observed during reward feedback. These results suggest that people with SZ and BD have opposite patterns of activation associated with reward anticipation but not reward receipt. Implications of these findings in regard to Research Domain Criteria-based classification of illness and the neurobiology of reward in psychosis are discussed.

A preliminary study on functional activation and connectivity during frustration in youths with bipolar disorder

OBJECTIVES

Frustration is associated with impaired attention, heightened arousal, and greater unhappiness in youths with bipolar disorder (BD) vs healthy volunteers (HV). Little is known about functional activation and connectivity in the brain of BD youths in response to frustration. This exploratory study compared BD youths and HV on attentional abilities, self-reported affect, and functional activation and connectivity during a frustrating attention task.

METHODS

Twenty BD (Mage  = 15.86) and 20 HV (Mage  = 15.55) youths completed an fMRI paradigm that differentiated neural responses during processing of frustrating feedback from neural responses during attention orienting following frustrating feedback. We examined group differences in (a) functional connectivity using amygdala, inferior frontal gyrus (IFG), and striatum as seeds and (b) whole-brain and regions of interest (amygdala, IFG, striatum) activation. We explored task performance (accuracy, reaction time), self-reported frustration and unhappiness, and correlations between these variables and irritability, depressive, and manic symptoms.

RESULTS

Bipolar disorder youths, relative to HV, exhibited positive IFG-ventromedial prefrontal cortex (vmPFC) connectivity yet failed to show negative striatum-insula connectivity during feedback processing. Irritability symptoms were positively associated with striatum-insula connectivity during feedback processing. Moreover, BD vs HV youths showed positive IFG-parahippocampal gyrus (PHG)/periaqueductal gray (PAG) connectivity and negative amygdala-cerebellum connectivity during attention orienting following frustration. BD was not associated with atypical activation patterns.

CONCLUSIONS

Positive IFG-vmPFC connectivity and striatum-insula decoupling in BD during feedback processing may mediate heightened sensitivity to reward-relevant stimuli. Elevated IFG-PAG/PHG connectivity in BD following frustration may suggest greater recruitment of attention network to regulate arousal and maintain goal-directed behavior.

Neurophysiological correlates of cognitive control and approach motivation abnormalities in adolescent bipolar disorders

Hypersensitivity to reward-relevant stimuli is theorized to be a core etiological factor in bipolar disorders (BDs). However, little is known about the role of cognitive control dysregulation within reward contexts in BDs, particularly during adolescence. Using electroencephalography (EEG), we explored alterations in cognitive control processes and approach motivation in 99 adolescents with (n=53) and without (n=46) BD during reward striving (target anticipation) and reward attainment (feedback) phases of a monetary incentive delay (MID) task. Time-frequency analysis yielded frontal theta and frontal alpha asymmetry as indices of cognitive control and approach motivation, respectively. Multilevel mixed models examined group differences, as well as age, sex, and other effects, on frontal theta and frontal alpha asymmetry during both phases of the task and on performance accuracy and reaction times. Healthy adolescent girls exhibited lower frontal theta than both adolescent girls with BD and adolescent boys with and without BD during reward anticipation and feedback. Across groups, adolescent boys displayed greater relative left frontal alpha activity than adolescent girls during reward anticipation and feedback. Behaviorally, adolescents with BD exhibited faster responses on both positively and negatively motivated trials versus neutral trials, whereas healthy adolescents had faster responses only on positively motivated trials; adolescents with BD were less accurate in responding to neutral trials compared to healthy controls. These findings shed light on normative and BD-specific involvement of approach motivation and cognitive control during different stages of reward processing in adolescence and, further, provide evidence of adolescent sex differences in these processes.

Transdiagnostic Prediction of Affective, Cognitive, and Social Function Through Brain Reward Anticipation in Schizophrenia, Bipolar Disorder, Major Depression, and Autism Spectrum Diagnoses

The relationship between transdiagnostic, dimensional, and categorical approaches to psychiatric nosology is under intense debate. To inform this discussion, we studied neural systems linked to reward anticipation across a range of disorders and behavioral dimensions. We assessed brain responses to reward expectancy in a large sample of 221 participants, including patients with schizophrenia (SZ; n = 27), bipolar disorder (BP; n = 28), major depressive disorder (MD; n = 31), autism spectrum disorder (ASD; n = 25), and healthy controls (n = 110). We also characterized all subjects with an extensive test battery from which a cognitive, affective, and social functioning factor was constructed. These factors were subsequently related to functional responses in the ventral striatum (vST) and neural networks linked to it. We found that blunted vST responses were present in SZ, BP, and ASD but not in MD. Activation within the vST predicted individual differences in affective, cognitive, and social functioning across diagnostic boundaries. Network alterations extended beyond the reward network to include regions implicated in executive control. We further confirmed the robustness of our results in various control analyses. Our findings suggest that altered brain responses during reward anticipation show transdiagnostic alterations that can be mapped onto dimensional measures of functioning. They also highlight the role of executive control of reward and salience signaling in the disorders we study and show the power of systems-level neuroscience to account for clinically relevant behaviors.

Neural responses to monetary incentives in bipolar disorder

Although behavioral sensitivity to reward predicts the onset and course of mania in bipolar disorder, the evidence for neural abnormalities in reward processing in bipolar disorder is mixed. To probe neural responsiveness to anticipated and received rewards in the context of bipolar disorder, we scanned individuals with remitted bipolar I disorder (n = 24) and well-matched controls (n = 24; matched for age and gender) using Functional Magnetic Resonance Imaging (FMRI) during a Monetary Incentive Delay (MID) task. Relative to controls, the bipolar group showed reduced NAcc activity during anticipation of gains. Across groups, this blunting correlated with individual differences in impulsive responses to positive emotions (Positive Urgency), which statistically accounted for the association of blunted NAcc activity with bipolar diagnosis. These results suggest that blunted NAcc responses during gain anticipation in the context of bipolar disorder may reflect individual differences in Positive Urgency. These findings may help resolve discrepancies in the literature on neural responses to reward in bipolar disorder, and clarify the relationship between brain activity and the propensity to experience manic episodes.

Steeper aging-related declines in cognitive control processes among adults with bipolar disorders

BACKGROUND

Little is known about the specificity of executive functioning (EF) decline in older adults with bipolar disorders (OABD), or the impact of bipolar disorders (BD) on the timing and slope of age-related declines in EF processes implicated in both BD etiology and normative aging-cognitive control (CC). This cross-sectional study investigated age-related CC decline in BD.

METHODS

Participants were 43 adults with BD (M age = 61.5, SD = 15.8; 86% male) and 45 Controls (M age = 65.2, SD = 12.2; 98% male). Two-way ANOVAs examined the effects of median-age-split and diagnostic groups on cognitive processes with established BD deficits-CC processes (mental flexibility and response inhibition), verbal learning, and verbal fluency.

RESULTS

The median-split-age-by-diagnostic-group interaction was significant for mental flexibility; OABD performed significantly worse than younger adults with BD and younger and older Controls. Exploratory multivariate adaptive regression spline characterized non-linear nature of aging-slope changes in mental flexibility for each diagnostic group, yielding an inflection point at older age and steeper subsequent decline in OABD versus Controls.

LIMITATIONS

This study is limited by a small sample (particularly for select neuropsychological measures) of mostly Caucasian men and BD diagnoses based on clinical interview and medical records review.

CONCLUSIONS

Compared to healthy older adults, OABD showed steeper age-related decline in mental flexibility-select EF processes that depend on the integrity of the CC system. Preliminary evidence links CC integrity to daily functioning in OABD; accelerated aging decline in CC may pose a mechanism for high risk of functional impairment and dementia in OABD.

Abnormal intrinsic cerebro-cerebellar functional connectivity in un-medicated patients with bipolar disorder and major depressive disorder

OBJECTIVE

The cerebellum plays an important role in depression. Cerebro-cerebellar circuits have been found to show aberrance in bipolar disorder (BD) and major depressive disorder (MDD). However, whether the cerebro-cerebellar connectivity contributes equally to the pathologic mechanisms of BD and MDD remains unknown.

METHODS

We recruited 33 patients with MDD, 32 patients with BD, and 43 healthy controls (HC). We selected six seed regions (three per hemisphere) in the cerebrum, corresponding to the affective, cognitive control, and default mode networks, to establish cerebro-cerebellar functional connectivity maps.

RESULTS

Relative to the HC, both the BD and MDD patients exhibited weaker negative connectivity between the right subgenual anterior cingulate cortex and the cerebellar vermis IV_V (p_BD = 0.03, p_MDD = 0.001) and weaker positive connectivity between the left precuneus and the left cerebellar lobule IX (p_BD = 0.043, p_MDD = 0.000). Moreover, the MDD patients showed weaker positive connectivity in the left precuneus-left cerebellar lobule IX circuit than the BD patients (p = 0.049). In addition, the BD patients showed weaker positive connectivity in the right dorsolateral prefrontal cortex-left cerebellar lobule Crus Ι circuit compared to the HC (p = 0.002) or the MDD patients (p = 0.013). Receiver operating characteristic curves analyses showed that the altered cerebro-cerebellar connectivities could be used to distinguish the patients from the HC with relatively high accuracy.

CONCLUSIONS

Our findings suggested that differences in connectivity of cerebro-cerebellar circuits, which are involved in affective or cognitive functioning, significantly contributed to BD and MDD.

Presentation and Neurobiology of Anhedonia in Mood Disorders: Commonalities and Distinctions

PURPOSE OF REVIEW

To focus on the clinical and behavioral presentation of anhedonia in mood disorders, as well as the differences and commonalities in the underlying neurocircuitry.

RECENT FINDINGS

Evidence suggests that depression is characterized by hypofunction of the reward system, while bipolar disorder manifests dysregulation of the behavioral activation system that increases goal-directed reward behavior. Importantly, strong evidence does not exist to suggest significant differences in anhedonia severity between depressed unipolar and bipolar patients, suggesting that there are more nuanced fluctuations in reward processing deficits in bipolar patients depending on their state. Both euthymic unipolar and bipolar patients frequently report residual reward dysfunction, which highlights the potential of reward processing deficits that give rise to the clinical symptom of anhedonia to be trait factors of mood disorders; however, the possibility that therapies are not adequately treating anhedonia could also explain the presence of residual symptoms. Reward processing represents a potential diagnostic and treatment marker for mood disorders. Further research should systematically explore the facets of reward processing in at-risk, affected, and remitted patients.

The International Society for Bipolar Disorders Task Force report on pediatric bipolar disorder: Knowledge to date and directions for future research

OBJECTIVES

Over the past two decades, there has been tremendous growth in research regarding bipolar disorder (BD) among children and adolescents (ie, pediatric BD [PBD]). The primary purpose of this article is to distill the extant literature, dispel myths or exaggerated assertions in the field, and disseminate clinically relevant findings.

METHODS

An international group of experts completed a selective review of the literature, emphasizing areas of consensus, identifying limitations and gaps in the literature, and highlighting future directions to mitigate these gaps.

RESULTS

Substantial, and increasingly international, research has accumulated regarding the phenomenology, differential diagnosis, course, treatment, and neurobiology of PBD. Prior division around the role of irritability and of screening tools in diagnosis has largely abated. Gold-standard pharmacologic trials inform treatment of manic/mixed episodes, whereas fewer data address bipolar depression and maintenance/continuation treatment. Adjunctive psychosocial treatment provides a forum for psychoeducation and targets primarily depressive symptoms. Numerous neurocognitive and neuroimaging studies, and increasing peripheral biomarker studies, largely converge with prior findings from adults with BD.

CONCLUSIONS

As data have accumulated and controversy has dissipated, the field has moved past existential questions about PBD toward defining and pursuing pressing clinical and scientific priorities that remain. The overall body of evidence supports the position that perceptions about marked international (US vs elsewhere) and developmental (pediatric vs adult) differences have been overstated, although additional research on these topics is warranted. Traction toward improved outcomes will be supported by continued emphasis on pathophysiology and novel therapeutics.

Winter birth, urbanicity and immigrant status predict psychometric schizotypy dimensions in adolescents

BACKGROUND

Urbanicity, immigration and winter-birth are stable epidemiological risk factors for schizophrenia, but their relationship to schizotypy is unknown. This is a first examination of the association of these epidemiological risk factors with positive schizotypy, in nonclinical adolescents, controlling for a range of potential and known confounders.

METHODS

We collected socio-demographics, life-style, family and school circumstances, positive schizotypy dimensions and other personality traits from 445 high school pupils (192 males, 158 immigrants) from 9 municipalities in Athens and Heraklion, Greece, which covered a range of host population and migrant densities. Using multivariate hierarchical linear regressions models, we estimated the association of schizotypy dimensions with: (1) demographics of a priori interest (winter-birth, immigrant status, urban characteristics), including family financial and mental health status; (2) factors resulting from principal component analysis (PCA) of the demographic and personal data; (3) factors resulting from PCA of the personality questionnaires.

RESULTS

Adolescent women scored higher on schizotypy than men. High anxiety/neuroticism was the most consistent and significant predictor of all schizotypy dimensions in both sexes. In the fully adjusted models, urbanicity predicted magical thinking and unusual experiences in women, while winter-birth and immigration predicted paranoid ideation and unusual experiences respectively in men.

CONCLUSIONS

These results support the continuum hypothesis and offer potential insights in the nature of risk conferred by winter-birth, urbanicity and immigration and the nature of important sex differences. Controlling for a wide range of potential confounding factors increases the robustness of these results and confidence that these were not spurious associations.