Mary Cannon

Royal College of Surgeons in Ireland, Dublin, Leinster, Ireland

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Publications (128)627.95 Total impact

  • World Psychiatry. 10/2014; 13(3).
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    ABSTRACT: An argument often used to support the view that psychotic experiences (PEs) in general population samples are a valid phenotype for studying the aetiology of schizophrenia is that risk factors for schizophrenia show similar patterns of association with PEs. However, PEs often co-occur with depression, and no study has explicitly tested whether risk factors for schizophrenia are shared between PEs and depression, or are psychopathology specific, while jointly modelling both outcomes.
    Psychological medicine. 09/2014; 44(12):2557-2566.
  • The American journal of psychiatry. 09/2014; 171(9):901-5.
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    ABSTRACT: Suicide is a leading cause of death among adolescents. Self-harm is the most important risk factor for suicide, yet the majority of self-harm does not come to the attention of health services. The purpose of this study was to establish the relative incidence of adolescent suicide, hospital-treated self-harm and self-harm in the community.
    Social Psychiatry and Psychiatric Epidemiology 06/2014; · 2.86 Impact Factor
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    ABSTRACT: Psychotic symptoms in the context of psychiatric disorders are associated with poor functional outcomes. Environmental stressors are important in the development of psychosis; however, distress may only be pathogenic when it exceeds an individual's ability to cope with it. Therefore, one interesting factor regarding poor functional outcomes in patients with psychotic symptoms may be poor coping. This paper aimed to address the question whether 1) psychotic symptoms are associated with poorer functioning and 2) whether poor coping moderated the association. In a clinical case-clinical control study of 106 newly-referred adolescent patients with non-psychotic psychiatric disorders, coping was investigated using the Adolescents Coping Scale. Severity of impairment in socio-occupational functioning was assessed with the Children's Global Assessment Scale. Patients with non-psychotic psychiatric disorders and additional psychotic symptoms (N = 50) had poorer functioning and were more likely to use avoidance-oriented coping compared to patients with non-psychotic psychiatric disorders without psychotic symptoms (N = 56). No differences were found with respect to approach-oriented coping. When stratifying for poor/good coping, only those adolescent patients with psychotic symptoms who applied poor coping (i.e. less use of approach-oriented coping styles [OR 0.24, p < 0.015] and more use of avoidance-oriented coping [OR 0.23, p < 0.034]) had poorer functioning. However, these interactions were not significant. Non-adaptive coping and poorer functioning were more often present in adolescents with non-psychotic psychiatric disorders and additional psychotic symptoms. Due to small subgroups, our analyses could not give definitive conclusions about the question whether coping moderated the association between psychotic symptoms and functioning. Improvement of coping skills may form an important target for intervention that may contribute to better clinical and functional outcomes in patients with psychotic symptoms.
    BMC Psychiatry 04/2014; 14(1):97. · 2.23 Impact Factor
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    ABSTRACT: Epilepsy has long been considered to be a risk factor for psychosis. However there is a lack of consistency in findings across studies on the effect size of this risk which reflects methodological differences in studies and changing diagnostic classifications within neurology and psychiatry. The aim of this study was to assess the prevalence of psychosis in epilepsy and to estimate the risk of psychosis among individuals with epilepsy compared with controls. A systematic review and meta-analysis was conducted of all published literature pertaining to prevalence rates of psychosis in epilepsy using electronic databases PUBMED, OVIDMEDLINE, PsychINFO and Embase from their inception until September 2010 with the following search terms: prevalence, incidence, rate, rates, psychosis, schizophrenia, schizophreniform illness, epilepsy, seizures, temporal lobe epilepsy. The literature search and search of reference lists yielded 215 papers. Of these, 58 (27%) had data relevant to the review and 157 were excluded following a more detailed assessment. 10% of the included studies were population based studies. The pooled odds ratio for risk of psychosis among people with epilepsy compared with controls was 7.8. The pooled estimate of prevalence of psychosis in epilepsy was found to be 5.6% (95% CI: 4.8-6.4). There was a high level of heterogeneity. The prevalence of psychosis in temporal lobe epilepsy was 7% (95% CI: 4.9-9.1). The prevalence of interictal psychosis in epilepsy was 5.2% (95% CI: 3.3-7.2). The prevalence of postictal psychosis in epilepsy was 2% (95% CI: 1.2-2.8). Our systematic review found that up to 6% of individuals with epilepsy have a co-morbid psychotic illness and that patients have an almost eight fold increased risk of psychosis. The prevalence rate of psychosis is higher in temporal lobe epilepsy (7%). We suggest that further investigation of this association could give clues to the aetiology of psychosis.
    BMC Psychiatry 03/2014; 14(1):75. · 2.23 Impact Factor
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    Ian Kelleher, Mary Cannon
    Schizophrenia Bulletin 01/2014; · 8.80 Impact Factor
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    ABSTRACT: Background This study investigated the prevalence of DSM-IV Axis 1 mental disorders, deliberate self-harm and suicidal ideation in a sample of Irish adolescents aged 11–13 years. Methods A total of 1131 students was surveyed for general psychopathology using the Strengths and Difficulties Questionnaire. Following this, a representative sample of 212 adolescents was assessed for mental disorders, deliberate self-harm and suicidal ideation using the Schedule for Affective Disorders and Schizophrenia for School-Aged Children. Results 14.6% of the sample met criteria for a borderline score and 6.9% for an abnormal score on the Strengths and Difficulties Questionnaire. Following clinical diagnostic interviews, 27.4% of participants received a current diagnosis of an Axis 1 disorder and 36.8% received a lifetime diagnosis, those rates falling to 15.4% and 31.2% respectively when specific phobias were excluded. Conclusions Findings from this study reveal that Irish adolescents aged 11–13 years are experiencing high levels of mental ill-health.
    Journal of Adolescence 01/2014; 37(1):1–9. · 2.05 Impact Factor
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    ABSTRACT: Objective Neurodevelopmental theories of psychosis highlight the potential benefits of early intervention, prevention, and/or preemption. How early intervention should take place has not been established, nor if interventions based on social learning principles can have preemptive effects. The objective was to test if a comprehensive psychosocial intervention can significantly alter psychotic symptom trajectories during adolescence – a period of heightened risk for a wide range of psychopathology. Method This study was a randomized controlled trial (RCT) of Multidimensional Treatment Foster Care (MTFC) for delinquent adolescent girls. Assessment of psychotic symptoms took place at baseline and then 6, 12, 18, and 24 months post-baseline using a standardized self-report instrument (Brief Symptom Inventory). A second source of information about psychotic symptoms was obtained at baseline or 12 months, and again at 24 months using a structured diagnostic interview (the Diagnostic Interview Schedule for Children [DISC]). Results Significant benefits for MTFC over treatment-as-usual for psychosis symptoms were observed over a 24-month period. Findings were replicated across both measures. Effects were independent of substance use and initial symptom severity, and persisted beyond the initial intervention period. Conclusion Ameliorating non-clinical psychotic symptoms trajectories beginning in early adolescence via a multifaceted psychosocial intervention is possible. Developmental research on non-clinical psychotic symptoms and their prognostic value should be complemented by more psychosocial intervention research aimed at modifying these symptom trajectories early in their natural history.
    Journal of the American Academy of Child & Adolescent Psychiatry. 01/2014;
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    ABSTRACT: Psychotic experiences are prevalent in community samples and are highly correlated with depressive symptoms. This study aimed to investigate the longitudinal associations between psychotic experiences and depressive symptoms between adolescence and young adulthood.
    PLoS ONE 01/2014; 9(8):e105758. · 3.53 Impact Factor
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    ABSTRACT: Recent community-based research has suggested that psychotic experiences act as markers of severity of psychopathology. There has, however, been a lack of clinic-based research. We wished to investigate, in a clinical sample of adolescents referred to a state-funded mental health service, the prevalence of (attenuated or frank) psychotic experiences and the relationship with (i) affective, anxiety and behavioural disorders, (ii) multimorbid psychopathology, (iii) global functioning, and (iv) suicidal behaviour. The investigation was a clinical case-clinical control study using semi-structured research diagnostic psychiatric assessments in 108 patients newly referred to state adolescent mental health services. Psychotic experiences were prevalent in a wide range of (non-psychotic) disorders but were strong markers of risk in particular for multimorbid psychopathology (Z = 3.44, p = 0.001). Young people with psychopathology who reported psychotic experiences demonstrated significantly poorer socio-occupational functioning than young people with psychopathology who did not report psychotic experiences, which was not explained by multimorbidity. Psychotic experiences were strong markers of risk for suicidal behaviour. Stratified analyses showed that there was a greatly increased odds of suicide attempts in patients with a major depressive disorder [odds ratio (OR) 8.89, 95% confidence interval (CI) 1.59-49.83], anxiety disorder (OR 15.4, 95% CI 1.85-127.94) or behavioural disorder (OR 3.13, 95% CI 1.11-8.79) who also had psychotic experiences compared with patients who did not report psychotic experiences. Psychotic experiences (attenuated or frank) are an important but under-recognized marker of risk for severe psychopathology, including multimorbidity, poor functioning and suicidal behaviour in young people who present to mental health services.
    Psychological Medicine 09/2013; · 5.59 Impact Factor
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    ABSTRACT: IMPORTANCE Up to 1 million persons die by suicide annually. However, a lack of risk markers makes suicide risk assessment one of the most difficult areas of clinical practice. OBJECTIVE To assess psychotic symptoms (attenuated or frank) as a clinical marker of risk for suicide attempt. DESIGN, SETTING, AND PARTICIPANTS Prospective cohort study of 1112 school-based adolescents (aged 13-16 years), assessed at baseline and at 3 and 12 months for self-reported psychopathology, psychotic symptoms, and suicide attempts. MAIN OUTCOMES AND MEASURES Suicide attempts at the 3- and 12-month follow-up and acute suicide attempts (defined as those occurring in the 2 weeks before an assessment). RESULTS Of the total sample, 7% reported psychotic symptoms at baseline. Of that subsample, 7% reported a suicide attempt by the 3-month follow-up compared with 1% of the rest of the sample (odds ratio [OR], 10.01; 95% CI, 2.24-45.49), and 20% reported a suicide attempt by the 12-month follow-up compared with 2.5% of the rest of the sample (OR, 11.27; 95% CI, 4.44-28.62). Among adolescents with baseline psychopathology who reported psychotic symptoms, 14% reported a suicide attempt by 3 months (OR, 17.91; 95% CI, 3.61-88.82) and 34% reported a suicide attempt by 12 months (OR, 32.67; 95% CI, 10.42-102.41). Adolescents with psychopathology who reported psychotic symptoms had a nearly 70-fold increased odds of acute suicide attempts (OR, 67.50; 95% CI, 11.41-399.21). Differences were not explained by nonpsychotic psychiatric symptom burden, multimorbidity, or substance use. In a causative model, the population-attributable fraction of suicide attempts would be 56% to 75% for psychotic symptoms. CONCLUSIONS AND RELEVANCE Adolescents with psychopathology who report psychotic symptoms are at clinical high risk for suicide attempts. More careful clinical assessment of psychotic symptoms (attenuated or frank) in mental health services and better understanding of their pathological significance are urgently needed.
    JAMA Psychiatry 07/2013; · 12.01 Impact Factor
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    ABSTRACT: OBJECTIVE The authors examined the development of psychotic experiences and psychotic disorders in a large population-based sample of young adults and explored their relationship to psychotic phenomena earlier in childhood. METHOD The authors conducted a longitudinal birth cohort study of individuals assessed with the semistructured Psychosis-Like Symptom Interviews at ages 12 and 18 years. RESULTS Of the 4,724 individuals interviewed at age 18, 433 (9.2%) had either suspected (N=203 [4.3%]) or definite (N=230 [4.9%]) psychotic experiences. Of these, 79 (1.7%) met criteria for a psychotic disorder, and of those, only 50% sought professional help. All psychotic outcomes were more likely in young women and in those from socioeconomically disadvantaged backgrounds. Of the participants who had psychotic experiences at age 12, 78.7% had remitted by age 18. The risk of psychotic disorders at age 18 was greater in those with suspected (odds ratio=5.6, 95% CI=2.6-12.1) and especially in those with definite (odds ratio=12.7, 95% CI=6.2-26.1) psychotic experiences at age 12, and also among those with psychotic experiences at age 12 attributed to sleep or fever or with nonpsychotic experiences such as depersonalization. The positive predictive values for increasing frequency of experiences at age 12 predicting psychotic disorders at age 18 ranged from 5.5% to 22.8%. CONCLUSIONS Despite evidence for a continuum of psychotic experiences from as early as age 12, positive predictive values for predicting psychotic disorders were too low to offer real potential for targeted interventions. Psychotic disorders in young adults are relatively uncommon, but they constitute an important unmet need for care given that half of the individuals in this study who met criteria for a psychiatric disorder had not sought help for these problems despite high levels of associated distress and impairment.
    American Journal of Psychiatry 05/2013; · 14.72 Impact Factor
  • Early Intervention in Psychiatry 05/2013; 7(2):103-8. · 1.65 Impact Factor
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    ABSTRACT: BACKGROUND: Deficits in working memory are widely reported in schizophrenia and are considered a trait marker for the disorder. Event-related potentials (ERPs) and imaging data suggest that these differences in working memory performance may be due to aberrant functioning in the prefrontal and parietal cortices. Research suggests that many of the same risk factors for schizophrenia are shared with individuals from the general population who report psychotic symptoms. METHODS: Forty-two participants (age range 11--13 years) were divided into those who reported psychotic symptoms (N = 17) and those who reported no psychotic symptoms, i.e. the control group (N = 25). Behavioural differences in accuracy and reaction time were explored between the groups as well as electrophysiological correlates of working memory using a Spatial Working Memory Task, which was a variant of the Sternberg paradigm. Specifically, differences in the P300 component were explored across load level (low load and high load), location (positive probe i.e. in the same location as shown in the study stimulus and negative probe i.e. in a different location to the study stimulus) and between groups for the overall P300 timeframe. The effect of load was also explored at early and late timeframes of the P300 component (250-430 ms and 430-750 ms respectively). RESULTS: No between-group differences in the behavioural data were observed. Reduced amplitude of the P300 component was observed in the psychotic symptoms group relative to the control group at posterior electrode sites. Amplitude of the P300 component was reduced at high load for the late P300 timeframe at electrode sites Pz and POz. CONCLUSIONS: These results identify neural correlates of neurocognitive dysfunction associated with population level psychotic symptoms and provide insights into ERP abnormalities associated with the extended psychosis phenotype.
    BMC Psychiatry 05/2013; 13(1):125. · 2.23 Impact Factor
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    ABSTRACT: OBJECTIVE: Psychotic symptoms are common in the population and index risk for a range of severe psychopathological outcomes. We wished to investigate functional connectivity in a community sample of adolescents who reported psychotic symptoms (the extended psychosis phenotype). METHOD: This study investigated intrinsic functional connectivity (iFC) during resting-state functional magnetic resonance imaging (fMRI; rs-fMRI). Following screening in schools, 11 non-treatment seeking, youth with psychotic symptoms (aged 11-13) and 14 community controls participated in the study. Seed regions of interest comprised brain regions previously shown to exhibit aberrant activation during inhibitory control in adolescents with psychotic symptoms. RESULTS: Relative to controls, adolescents with psychotic symptoms exhibited reduced iFC between regions supporting inhibitory control. Specifically, they showed weaker iFC between the right inferior frontal gyrus (IFG) and the cingulate, IFG and the striatum, anterior cingulate and claustrum, and precuneus and supramarginal gyrus. Conversely, the psychotic symptoms group exhibited stronger iFC between the superior frontal gyrus and claustrum and IFG and lingual gyrus. CONCLUSION: The present findings are the first to reveal aberrant functional connectivity in resting-state networks in a community sample of adolescents with psychotic symptoms and suggest that disruption in integration between distributed neural networks (particularly between prefrontal, cingulate and striatal brain regions) may be a key neurobiological feature of the extended psychosis phenotype.
    Acta Psychiatrica Scandinavica 04/2013; · 4.86 Impact Factor
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    ABSTRACT: OBJECTIVE Using longitudinal and prospective measures, the authors assessed the relationship between childhood trauma and psychotic experiences, addressing the following questions: 1) Does exposure to trauma predict incident psychotic experiences? 2) Does cessation of trauma predict cessation of psychotic experiences? 3) What is the direction of the relationship between childhood trauma and psychotic experiences? METHOD This was a nationally representative prospective cohort study of 1,112 school-based adolescents 13-16 years of age, assessed at baseline and at 3-month and 12-month follow-ups for childhood trauma (physical assault and bullying) and psychotic experiences. RESULTS A bidirectional relationship was observed between childhood trauma and psychosis, with trauma predicting psychotic experiences over time and vice versa. However, even after accounting for this bidirectional relationship with a number of strict adjustments (only newly incident psychotic experiences occurring over the course of the study following exposure to traumatic experiences were examined), trauma was strongly predictive of psychotic experiences. A dose-response relationship was observed between severity of bullying and risk for psychotic experiences. Moreover, cessation of trauma predicted cessation of psychotic experiences, with the incidence of psychotic experiences decreasing significantly in individuals whose exposure to trauma ceased over the course of the study. CONCLUSIONS After a series of conservative adjustments, the authors found that exposure to childhood trauma predicted newly incident psychotic experiences. The study also provides the first direct evidence that cessation of traumatic experiences leads to a reduced incidence of psychotic experiences.
    American Journal of Psychiatry 04/2013; · 14.72 Impact Factor
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    ABSTRACT: BACKGROUND: Deficits in the mismatch negativity (MMN) and P3a components are the most reliable and robust findings in schizophrenia. These abnormalities have also been recently documented in individuals clinically at risk for psychosis, indicating that the MMN may be a potential biomarker for psychosis. However, the at risk samples included in MMN studies are characterised by pre-existing clinical symptomatology and significant functional decline which are related to MMN amplitude. These factors may be potential confounds in determining whether deficient MMN is present prior to clinical manifestation of the disorder. Therefore, investigating the MMN in the extended psychosis phenotype comprising adolescents with psychotic symptoms from the general population may provide important information on whether abnormal MMN is apparent in the earliest stages of risk. METHODS: Thirty six adolescents completed a duration deviant MMN task. Fourteen adolescents with psychotic symptoms comprised the at risk group and 22 with no psychotic symptoms comprised the Controls. The task consisted of 85% standard tones (25 ms) and 15% deviant tones (50 ms). The groups were compared on MMN and P3a amplitude and latency across frontocentral and temporal electrodes. RESULTS: Adolescents with psychotic symptoms were characterised by a reduction in MMN amplitude at frontal and temporal regions compared to the controls. CONCLUSIONS: This is the first study to demonstrate impaired auditory discrimination for duration deviant tones in nonclinical adolescents with psychotic symptoms. These findings suggest that MMN amplitude may be a possible biomarker for vulnerability to psychosis.
    BMC Psychiatry 02/2013; 13(1):45. · 2.23 Impact Factor
  • Ian Kelleher, Mary Cannon
    The British journal of psychiatry: the journal of mental science 02/2013; 202:152-3. · 6.62 Impact Factor
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Publication Stats

5k Citations
627.95 Total Impact Points


  • 2006–2014
    • Royal College of Surgeons in Ireland
      • Department of Psychiatry
      Dublin, Leinster, Ireland
  • 2005–2014
    • Beaumont Hospital
      Dublin, Leinster, Ireland
  • 2012
    • National University of Ireland, Maynooth
      • Department of Psychology
      Maynooth, L, Ireland
    • St. Vincent’s Hospital, Fairview
      Dublin, Leinster, Ireland
  • 2001–2006
    • King's College London
      • Department of Psychological Medicine
      London, ENG, United Kingdom
  • 2003
    • McLean Hospital
      Cambridge, Massachusetts, United States
  • 1998
    • University of Nottingham
      • Division of Psychiatry
      Nottingham, ENG, United Kingdom
  • 1997–1998
    • Maastricht University
      • Psychiatrie en Neuropsychologie
      Maastricht, Provincie Limburg, Netherlands
  • 1994
    • Saint John of God Hospitaller Services
      Dublin, Leinster, Ireland