To what extent do studies of paranoia in the non-clinical population inform psychological interventions for psychosis?

Introduction

Research into paranoia in non-clinical populations has enriched our understanding of this phenomenon and informed psychological interventions for psychosis. Paranoia is defined as an interpersonal experience: a fear that others intend to cause you physical, psychological or social harm (Freeman & Garety, 2000; Freeman, Pugh et al., 2008). Within this essay the term ‘psychosis’ refers to a complex concept, including hallucinations, voice hearing and delusions, accompanied by a negative impact on social functioning (Fowler, Garety & Kuipers, 1995; Morrison, Renton, Dunn, Williams, & Bentall, 2004). Persecutory delusions represent the severe end of the paranoia continuum in the general population and are often an experience of psychosis (Freeman, 2006). Delusions are beliefs that are “implausible, unfounded, strongly held, not shared by others, distressing and preoccupying” (Freeman, 2007, p. 426).

This essay aims to consider the extent to which studies of paranoia in the non-clinical population have informed psychological interventions for psychosis, particularly focusing on Cognitive Behavioural Therapy (CBT). Mindfulness based approaches and Acceptance and Commitment Therapy (ACT) will also briefly be considered (Gaudiano, 2015). Studies of paranoia in the non-clinical population may also have informed other psychological interventions, such as family interventions (Haddock & Spaulding, 2013; Pharoah, Rathbone, Mari, & Streiner, 2003); computer avatar interventions (Leff, Williams, Huckvale, Arbuthnot, & Leff, 2014) and interventions developed from user-led movements such as the ‘hearing voices movement’ (Longden, Corstens, Escher & Romme, 2012). Due to the limited scope of this essay these interventions and their links to studies of paranoia in the non-clinical population will not be examined.

Paranoia in the Non-clinical Population

Why Study Paranoia?

Paranoia is associated with reduced social functioning, suicidal ideation, greater use of psychiatric medication and increased use of mental health services (Freeman et al., 2011). Therefore, the experience of paranoia has wide implications for health, wellbeing and social functioning (Freeman et al., 2011). Within the literature the ‘non-clinical population’ refers to people who have not received a psychiatric diagnosis (Freeman, 2006).

The Continuum

Historically, psychosis has been viewed as distinctly different to ‘normal’ experiences (Morrison et al., 2004). However, paranoid beliefs in the general population have a higher prevalence than psychotic disorders, suggesting psychosis exists on a continuum, with a distribution in the general population (Bentall, 1994; Stefanis et al., 2002; Strauss, 1969, cited in Van Os, Hanssen, Bijl, & Ravelli, 2000). The continuum idea is fundamental to understanding clinical experiences of psychosis as it implies delusions are not qualitatively different from other beliefs (Freeman, 2007; Johns & Van Os, 2001).

Prevalence

Paranoia has been found in the non-clinical adult population (Scott, Chant, Andrews & McGrath, 2006). Freeman et al. (2005) found over half the participants in a non-clinical sample endorsed ‘needing to be on guard against others’ during a one-week period and 10-30% had persecutory thoughts, ranging from mild to severe. Perceived lack of control over thoughts was associated with a higher occurrence of thoughts, and beliefs held with more conviction were associated with greater distress (Freeman et al., 2005). Other research has suggested the distribution of paranoia in the general population fits an exponential curve, with ‘most people having few paranoid thoughts and few people having many’ (Bebbington et al., 2013, p. 419). Johns et al. (2004) surveyed over 8000 people and found 20% thought people were against them and 10% thought people had deliberately acted to harm them.

Paranoia has been found in the older adult population (Forsell & Henderson et al., 1998; Ostling & Skoog, 2002) and childhood and adolescence (Laurens, Hobbs, Sunderland, Green, & Mould, 2012; Wigman et al., 2011). Up to 18.2% of a sample of Chinese undergraduates reported paranoid ideation at least once a week (Chan et al., 2011). Wong, Freeman and Hughes (2014) found ‘mistrustful’ children in the UK and Hong Kong showed higher levels of anxiety, low self-esteem and aggression. Delusions have also been discovered in the non-clinical population (Eaton, Romanoski, Anthony, & Nestadt, 1991; Freeman, 2006; Peters, Joseph & Garety, 1991). These studies suggest experiences of paranoia occur across ages and cultures.

Limitations

Despite evidence of paranoia in the non-clinical population, self-select survey methods may inadvertently recruit participants experiencing psychological difficulties (Freeman et al., 2005) or participants experiencing psychological difficulties may be less likely to respond (Van Os & Verdoux, 2003). Therefore, generalisations from prevalence studies should be tentative. Mullen (2003) claimed the language used by Peters et al. (1991) meant delusions were ‘toned down’ so the conclusion that delusions are on a continuum with ‘normal beliefs’ was questionable (p. 507). Freeman et al. (2005) highlight that many prevalence studies only report whether an experience is present or not, therefore no causal inferences can be made. Further, some “paranoid” thoughts may be based in reality so may not truly be examples of paranoia (Freeman et al., 2005; Mullen, 2003).

Experimental Studies 

To overcome difficulties with self-select survey methods, experimental studies have been undertaken with non-clinical populations. Ellett and Chadwick (2007) used a task with self-awareness and failure as variables. High levels of self-awareness in addition to ambiguous feedback or explicit failure were associated with higher levels of paranoia. The researchers proposed paranoid thoughts increased with greater self-focused attention, in line with the ‘self-as-target bias’, which claims people who focus on themselves assume others are doing the same (Ellett & Chadwick, 2007; Fenigstein & Vanable, 1992). This research supported the idea of the self-serving bias, which states paranoia has a self-protective function as people attribute negative outcomes to external causes (Bentall, 1994; Bentall et al., 2009). This idea was supported when people with high self-awareness completed a prior self-affirmation task and their experience of paranoia reduced (Kingston & Ellett, 2014).

Virtual Reality

Virtual reality research is beneficial as ‘real-time’ experiences of paranoia can be measured, and the characters behave in ways deemed to be neutral by consensus, meaning paranoid thoughts are more likely to be unfounded (Freeman, Gittins et al., 2008; Freeman, Pugh et al., 2008). Freeman, Gittins et al. (2008) created a virtual experience of an underground train to capture misinterpretations of facial expressions and concluded state paranoia could be triggered in environments that lacked objective threat in the non-clinical population. Using virtual reality, researchers have suggested a connection between paranoia in the non-clinical population and persecutory delusions within psychosis due to interpersonal sensitivity, anxiety and traumatic events predicting paranoia in both populations (Freeman et al., 2003; Freeman, Pugh et al., 2008; Freeman, Pugh, Vorontsova, Antley, & Slater, 2010).

Prisoner’s Dilemma Game

In the Prisoner’s Dilemma Game (PDG) two players are forced to choose between collaborating or competing against each other (Ellett, Allen-Crooks, Stevens, Wildschut, & Chadwick, 2013). If both players choose to compete the potential outcomes are worse than if they choose to collaborate whereas, if one chooses to compete and the other chooses to work collaboratively, the one who decided to compete gains greater outcomes (Ellett et al., 2013, Freeman & Garety, 2000). The PDG is interpersonal, concerned with issues of threat and trust, and is ambiguous, therefore useful for studying paranoia (Ellett et al 2013). Using the PDG, Ellett et al. (2013) found people with higher state paranoia were more likely to make a competitive choice when they believed they were playing against another person, highlighting the interpersonal nature of paranoia.

Links to Psychosis

To consider the extent to which studies of paranoia in the non-clinical population inform psychological interventions for psychosis, the links between non-clinical and clinical levels of paranoia need to be considered. Dominguez (2011) discovered that the more ‘psychosis-like’ experiences persisted over time during adolescence, the more likely it was those individuals would be diagnosed with clinical psychosis later in life. Other studies have found experiences of hallucinations and delusions in adolescence predicted later development of psychosis (Linscott & Van Os, 2013; Poulton et al., 2000).

Despite some limitations, the body of research described above has greatly influenced our understanding of psychosis from a psychological perspective and contributed to psychosis being conceptualised within a cognitive model.

Cognitive Model of Psychosis

The cognitive model is based on the premise that interpretations of events, rather than events themselves, contribute to emotional distress (Beck, Rush, Shaw & Emery, 1979). This has been applied to the conceptualisation of psychosis where it is thought that interpretations of experiences of psychosis determine whether an individual becomes distressed by their experience (Chadwick, 2006; Garety, Kuipers, Fowler, Freeman, & Bebbington, 2001; Morrison et al., 2001; Morrison, Wells & Nothard, 2000, 2002).

Studies of paranoia in the non-clinical population have informed this cognitive conceptualisation of psychosis. For example, Freeman, Gittins et al. (2008) explain that, in the context of anxiety, perceptual abnormalities, for example innocuous bodily sensations, can trigger paranoia. The non-clinical literature has also elucidated factors making the development of psychosis more likely. Positive beliefs about paranoia (for example, beliefs about experiences adding meaning to one’s life) were found to predict vulnerability to hallucinations (Morrison et al., 2005; 2001; Morrison, Wells, & Nothard, 2000, 2002). The addition of negative beliefs, such as beliefs about experiences being uncontrollable, determine whether someone feels distressed and seeks help, thus reaching a ‘clinical’ level of psychosis (Morrison, Wells & Nothard, 2000; 2002).

The cognitive model for psychosis also suggests distress is maintained by unhelpful ways of thinking and behaving, such that alternative explanations for unusual experiences are not considered (Bucci & Tarrier, 2016, Chadwick, 2006).

CBT Interventions for Psychosis

Together with behavioural theories, the cognitive model forms the basis for CBT for psychosis, which has been shown to be an effective psychological intervention with moderate effect sizes (Steel, Tarrier, Stahl, & Wykes, 2012; Zimmermann, Favrod, Trieu, & Pomini, 2005). The National Institute for Health and Care Excellence [NICE] (2014) recommends at least sixteen sessions of CBT delivered on a one to one basis for first episode psychosis and severe and enduring psychosis, alongside medication. Various elements of CBT for psychosis will be explored next, with links to the literature considered.

Normalising

Individuals experiencing long term psychosis are likely to have a diagnosis of ‘Schizophrenia’, which can be stigmatising (Corrigan, Watson, & Barr, 2006). Collaboratively discussing new ways of understanding one’s “disorder” can serve to reduce feelings of self-blame and stigma (Baba et al., 2017; Chadwick, Trower & Birchwood, 1996). Within the early stages of CBT the prevalence of unusual experiences, for example paranoia, in the non-clinical population is explored in order to modify unhelpful interpretations about the meaning of unusual experiences (Turkington, Kingdon & Weiden, 2006). Normalising has been shown to reduce negative beliefs about paranoia, and distress (Wood, Birtel, Alsawy, Pyle, & Morrison, 2014).

Within non-clinical populations traumatic events have been linked with paranoia (Freeman et al., 2010). Within CBT, stress-vulnerability models can be explored to help people consider the interaction of personal vulnerability factors, coping skills, stressful life events and environmental protective factors (Nuechterlain, Parasuraman & Jiang, 1983, Chadwick, 2006). An individualised formulation can help people be less self-blaming if they realise they had a pre-existing vulnerability to psychosis and then experienced stressful life events beyond their control (Chadwick, 2006; Dudley, Kuyken and Padesky, 2011). These ideas suggest studies into paranoia in the non-clinical population have been utilised in psychological interventions for psychosis.

Beliefs about Experiences

Research with a non-clinical population has shown people report differences in degrees of conviction in paranoid thoughts, and levels of preoccupation and distress associated with their thoughts (Ellett, Lopes & Chadwick, 2003; Freeman et al., 2005; Morrison et al., 2005). It is therefore useful to assess these factors within CBT, along with individual beliefs about the identity, perceived power and intent of voices, and the control the person feels they have over their voices (Chadwick et al., 1996, Fowler et al, 1995; Steel, 2008).

To challenge beliefs about voices being uncontrollable, CBT involves triggering voices in session then stopping them using distraction, for example by reading aloud, or gaining a sense of control over voices by suggesting they fade away (Chadwick & Birchwood 1994; Fowler & Morley, 1989). Cognitive therapy has been shown to reduce the degree of conviction in the power and superiority of voices, and reduce compliance behaviour in people experiencing command hallucinations (Trower et al., 2004). If someone holds positive beliefs about paranoia, for example that it helps them stay safe, these beliefs can be explored and re-evaluated within CBT (Murphy et al., 2017). It could be argued that non-clinical research has highlighted the role of beliefs about experiences in the development and maintenance of paranoia and this has strengthened the idea that beliefs about experiences need to be targeted in CBT.

Reasoning Biases

Paranoia in the general population is associated with reasoning biases, particularly jumping to conclusions, and reduced analytic reasoning (Freeman, Evans & Lister., 2012; Freeman, Gittins et al., 2008; So et al., 2012). In a comparison between people with high and low paranoia in a non-clinical sample, the high paranoia group perceived more hostility and blame in an ambiguous social situation (Combs et al., 2013). Similar reasoning biases have been found in the clinical population as people with persecutory delusions use rational reasoning styles less frequently (Freeman, Lister & Evans, 2014). Reasoning biases contribute to ‘belief inflexibility’, which is associated with higher conviction in delusions (Freeman et al., 2004; Garety et al., 2005).

CBT for psychosis involves monitoring thoughts, feelings and behaviours to establish whether people interpret neutral events in negative ways, then enabling people to consider alternative, less threatening, explanations (Fowler et al., 1995; Morrison et al., 2004).

Within CBT for psychosis, one approach to working with delusions involves helping people recognise their delusion is a belief or interpretation, using the Antecedents-Beliefs-Consequences model (Chadwick et al., 1996, p. 47). Subsequently, people are encouraged to discover evidence that does not fit with their delusion or, if that proves difficult, to consider how hypothetical contradictions would impact on their beliefs (Chadwick et al., 1996; p. 119).

Researchers delivered a brief reasoning intervention to people experiencing delusions and found reductions in paranoia, reduced use of the ‘jumping to conclusions’ reasoning bias and increased belief flexibility (Garety et al., 2015). It could be argued that studies of paranoia in the non-clinical population helped informed these interventions as they challenged the idea that delusions were qualitatively different beliefs, allowing them to be targeted within CBT (Morrison et al., 2004).

Negative Self-Evaluations

Ellett et al., (2003) suggest low self-esteem is associated with higher paranoid ideation in the non-clinical population. Freeman and Garety (2014) explain negative views of the self can lead to feeling different, inferior and vulnerable, and paranoia is more likely to develop when someone perceives themselves as vulnerable (p. 1181). There have been similar findings with clinical samples, suggesting negative views of the self are influential in maintaining psychosis (Bentall et al., 2009; Garety & Freeman, 2013; Tiernan, Tracey & Shannon, 2014). Fowler et al. (2012) suggested the link between depressed mood and paranoia was mediated by negative views of self and others, low self-esteem and self-criticism. However, they acknowledge that, due to the longitudinal design, the links are only correlational and suggest an experimental design would help control for confounding variables. Another study with a clinical population displaying early signs of psychosis found the more someone held negative beliefs about the self the more they believed they ‘deserved’ persecution (Morrison et al., 2015).

In terms of intervention, Chadwick (2003) outlines the ‘two chairs method’ where people are encouraged to experience their usual negative self-view then physically move seats within session to experience an alternative positive self-view. People are then encouraged to notice experiences that do not fit with their negative self-view (Chadwick, 2003). A life review can help reframe misinterpretations of adverse life events that may have contributed to a negative self-view (Curr & McNulty, 2006). If someone has experienced multiple episodes of psychosis and been labelled as a ‘patient’, helping them view themselves as ‘survivor’ instead of ‘victim’ may be helpful (Curr & McNulty, 2006). Addressing negative thoughts about the self has also been shown to help people overcome avoidance of busy places and this is increasingly a focus in CBT for psychosis (Freeman et el., 2014; Freeman, Waller et al., 2015). In summary, interventions targeting self-esteem appear to be influenced by studies of paranoia in the non-clinical population. CBT also focuses on helping people make changes to the behaviours maintaining their difficulties (Tully, Wells & Morrison, 2017; Westbrook, Kennerley & Kirk, 2007).

Behavioural Experiments

It has been found that people in the non-clinical population who attach meaning to their paranoid thoughts feel more distressed and act accordingly, for example by using avoidance (Ellett et al., 2003; Freeman et al., 2005; Freeman et el., 2014). Avoidance prevents the disconfirmation of beliefs and is a common maintenance factor in anxiety disorders (Clark & Wells, 1995; Westbrook et al., 2007). Within the clinical population, people experiencing psychosis have been found to use avoidance as a coping strategy (Freeman et al., 2014, Tully et al., 2017). Within interventions for psychosis, overcoming avoidance is a target for change (Van der Gaag, Nieman, & Van den Berg, 2013). Behavioural experiments are used to help people overcome avoidance and test out beliefs about voices (Chadwick, 2006; Menon et al., 2015). These behavioural approaches demonstrate how research into paranoia in the non-clinical population has been used to support the development of interventions for psychosis.

Rumination and Worry

Rumination has been found to maintain paranoia (Martinelli, Cavanagh & Dudley, 2013). One study induced paranoia in non-clinical participants and found evidence that ruminative self-focus maintained paranoia whereas mindful self-focus reduced levels of paranoia (McKie, Askew & Dudley, 2017). In a non-clinical population, Freeman, Pugh et al. (2008) identified worry as important in the development of paranoia. A longitudinal study showed the emergence of new paranoid thoughts was predicted by the presence of worry in both non-clinical and clinical populations (Freeman et al., 2012). This suggests non-clinical research informs areas for research with clinical populations. In a subsequent clinical trial a six-session worry reduction intervention plus standard care was compared with standard care alone and the addition of the worry reduction intervention led to significant reductions in worry and delusions (Freeman, Dunn et al., 2015). Changes in worry mediated most of the change in delusions, suggesting worry is an important area to target in psychological interventions for psychosis (Freeman, Dunn et al., 2015).

Mindfulness and ACT

Research into non-clinical paranoia has also informed the development of ‘third wave’ approaches for psychosis, such as mindfulness and ACT (Kabat-Zinn, 2003; Sugiura, 2004). These approaches encourage people to relate to experiences of voices and delusions in a different way, for example by increasing awareness of the experiences then fostering distance from them, known as ‘decentring’ (Lau, Bishop & Segal et al., 2006). This reduces distress as people learn their experiences are not reflections of themselves (Chadwick, Barnbrook & Newman-Taylor, 2017). During interventions, people experiencing voices or delusions are encouraged to practice skills to help them view their experiences as passing events and foster acceptance of unusual experiences (Chadwick et al., 2007; Gaudiano, 2015).

ACT has been found to reduce the believability of thoughts and reduce re-admission to hospital for acute patients experiencing psychosis (Bach & Hayes, 2002; Bach, Gaudiano, Hayes & Herbert, 2013). However, results with medication-resistant psychosis have been mixed: clinically significant improvements in positive symptoms and hallucination distress were shown when ACT was compared with befriending, but befriending led to greater improvements in delusion distress (Shawyer et al, 2017).

Research into paranoia in non-clinical populations has highlighted the role of beliefs and responses to experiences when determining levels of distress (Freeman et al., 2005; Morrison, Wells & Nothard, 2000; 2002). It could therefore be argued that both mindfulness and ACT interventions for psychosis are informed by studies of non-clinical paranoia as they aim to change how one responds to their experiences (Kabat-Zinn, 2003; Lau, Bishop & Segal et al., 2006).

Discussion

Efficacy of CBT

Around fifty percent of people who have completed CBT for psychosis show limited improvement (O’Keeffe, Conway, & McGuire, 2017; Turkington, & McKenna, 2003). One view that may account for why half of people show limited improvement, is the view that delusions are actually distinct from other beliefs and not on a continuum with ‘normal’ experience (Jaspers, 1963, cited in Jones, Delespaul, & Van Os, 2003; Mullen, 2003). If delusions are distinct from other beliefs, this suggests findings from the non-clinical population have limited generalisability to people with psychosis (Mullen, 2003).

Research with Clinical Populations

Many studies informing psychological interventions have used clinical samples of people with ‘chronic treatment-resistant psychosis who have been stabilised on anti-psychotic medication’ (Haddock & Lewis, 2005, p. 697). Studies into non-clinical populations involve participants who have no formal diagnosis, are not prescribed anti-psychotic medication and who are not debilitated by paranoia (Freeman, 2006). It could therefore be argued that psychological interventions for psychosis have been informed by studies into maintenance processes in the clinical population more than studies of paranoia in the non-clinical population and that these populations are very different.

Research into paranoia in the non-clinical population has highlighted important factors involved in the development of clinical paranoia, for example, interpersonal sensitivity and anxiety (Freeman, Pugh et al., 2008). It could therefore be argued that this body of research has informed psychological interventions for people at risk of developing psychosis to a great extent (Morrison et al., 2015). However, with regard to severe and enduring psychosis, studies of paranoia in non-clinical populations may have informed interventions indirectly, for example, by highlighting areas to investigate in clinical populations. These clinical studies have subsequently informed interventions (Freeman, Dunn et al., 2015).

CBT for Anxiety and Depression

Another view is that the continuum idea led to researchers recognising that people with psychosis are no different to people with other disorders, for example, anxiety disorders (Morrison et al., 2004). This meant established CBT models into maintenance factors and their associated interventions were applied to psychosis (Beck et al., 1979; Chadwick et al., 1996; Morrison et al, 2004; Westbrook et al., 2007). On the one hand it could be said that the body of research into CBT for anxiety disorders and depression has greatly informed psychological interventions for psychosis, rather than studies of paranoia in the non-clinical population. It could also be argued that, without the continuum view, these models would not have been applied to psychosis and psychosis may have still been considered ‘untreatable’ (Chadwick et al., 1996; Morrison et al., 2004).

Conclusion

In conclusion, the continuum view of psychosis, derived from studies of paranoia in the non-clinical population, appears to have informed psychological interventions to a great extent, particularly by informing the cognitive model and the development of CBT for psychosis. Studies of paranoia in the non-clinical population have highlighted risk factors for the development of psychosis, for example, interpersonal sensitivity, anxiety and traumatic events (Freeman, Pugh et al., 2008, Freeman et al., 2010). Research into non-clinical paranoia has also informed interventions for psychosis by highlighting areas to focus on during intervention, for example, normalisation, beliefs about experiences, reasoning biases, negative self-evaluations, unhelpful behaviours, rumination and worry. Alternatives to the continuum view, along with other factors that have informed psychological interventions (studies with clinical populations and research into CBT for anxiety disorders) have been considered.

Despite these alternative views, it appears viewing psychosis as an exaggeration of ‘normal’ experience contributed to the realisation that people experiencing psychosis are no different from other people, which challenged the view that psychosis was ‘untreatable’ with psychological interventions. This has contributed to reducing stigma for people with psychosis (Baba et al., 2017). In conclusion, studies of paranoia in the non-clinical population have informed psychological interventions for psychosis to a great extent and in a meaningful way. However, findings show that around fifty percent of people who have completed CBT for psychosis show limited improvement (O’Keeffe, Conway, & McGuire, 2017; Turkington, & McKenna, 2003), suggesting further research into non-clinical and clinical populations is required, in order to improve the efficacy of this psychological intervention for psychosis.

References

Baba, Y., Nemoto, T., Tsujino, N., Yamaguchi, T., Katagiri, N., & Mizuno, M. (2017). Stigma toward psychosis and its formulation process: prejudice and discrimination against early stages of schizophrenia. Comprehensive psychiatry, 73, 181-186.

Bach, P., & Hayes, S. C. (2002). The use of acceptance and commitment therapy to prevent the rehospitalization of psychotic patients: A randomized controlled trial. Journal of consulting and clinical psychology, 70(5), 1129-1138.

Bach, P., Gaudiano, B. A., Hayes, S. C., & Herbert, J. D. (2013). Acceptance and commitment therapy for psychosis: intent to treat, hospitalization outcome and mediation by believability. Psychosis, 5(2), 166-174.

Bebbington, P. E., McBride, O., Steel, C., Kuipers, E., Radovanovič, M., Brugha, T., … & Freeman, D. (2013). The structure of paranoia in the general population. The British Journal of Psychiatry, 202(6), 419-427.

Beck, A. T., Rush, A. J., Shaw, B. F., & Emery, G. (1979). Cognitive therapy of depression. New York: Guildford Press

Bentall, R. (1994). Cognitive Biases and Abnormal Beliefs: Towards a model of persecutory delusions. In A. S. David and J. Cutting (Eds.), The Neuropsychology of Schizophrenia. London: Lawrence Erlbaum Associates.

Bentall, R. P., Rowse, G., Shryane, N., Kinderman, P., Howard, R., Blackwood, N., … & Corcoran, R. (2009). The cognitive and affective structure of paranoid delusions: a transdiagnostic investigation of patients with schizophrenia spectrum disorders and depression. Archives of general psychiatry, 66(3), 236-247.

Bucci, S., & Tarrier, N. (2016). A cognitive behavioural case formulation approach to the treatment of psychosis. In: N. Tarrier & J. Johnson (Eds.), Case Formulation in Cognitive Behaviour Therapy: The Treatment of Challenging and Complex Cases: Second Edition, Sussex: Routledge.

Carr, A., & McNulty, M. (Eds.). (2006). The handbook of adult clinical psychology: an evidence based practice approach. Routledge.

Chadwick, P. (2003). Two chairs, self-schemata and a person based approach to psychosis. Behavioural and Cognitive Psychotherapy, 31(4), 439-449.

Chadwick, P. (2006). Person-based cognitive therapy for distressing psychosis. Sussex: John Wiley & Sons.

Chadwick, P., & Birchwood, M. (1994). The omnipotence of voices. A cognitive approach to auditory hallucinations. The British Journal of Psychiatry, 164(2), 190-201.

Chadwick, P., Barnbrook, E., & Newman-Taylor, K. (2007). Responding mindfully to distressing voices: links with meaning, affect and relationship with voice. Journal of the Norwegian Psychological Association, 44, 581-588.

Chan, R. C., Li, X., Lai, M. K., Li, H., Wang, Y., Cui, J., … & Raine, A. (2011). Exploratory study on the base-rate of paranoid ideation in a non-clinical Chinese sample. Psychiatry research, 185(1), 254-260.

Combs, D. R., Finn, J. A., Wohlfahrt, W., Penn, D. L., & Basso, M. R. (2013). Social cognition and social functioning in nonclinical paranoia. Cognitive neuropsychiatry, 18(6), 531-548.

Corrigan, P. W., Watson, A. C., & Barr, L. (2006). The self–stigma of mental illness: Implications for self–esteem and self–efficacy. Journal of social and clinical psychology, 25(8), 875-884.

Dominguez, M. D. G., Wichers, M., Lieb, R., Wittchen, H. U., & van Os, J. (2011). Evidence that onset of clinical psychosis is an outcome of progressively more persistent subclinical psychotic experiences: an 8-year cohort study. Schizophrenia bulletin, 37(1), 84-93.

Dudley, R., Kuyken, W., & Padesky, C. A. (2011). Disorder specific and trans-diagnostic case conceptualisation. Clinical Psychology Review, 31(2), 213-224.

Eaton, W. W., Romanoski, A., Anthony, J. C., & Nestadt, G. (1991). Screening for psychosis in the general population with a self-report interview. The Journal of nervous and mental disease, 179(11), 689-693.

Ellett, L. Y. N., Lopes, B., & Chadwick, P. (2003). Paranoia in a nonclinical population of college students. The Journal of nervous and mental disease, 191(7), 425-430.

Ellett, L., Allen-Crooks, R., Stevens, A., Wildschut, T., & Chadwick, P. (2013). A paradigm for the study of paranoia in the general population: The Prisoner’s Dilemma Game. Cognition & emotion, 27(1), 53-62.

Ellett,L. & Chadwick, P. (2007). Paranoid cognitions, failure, and focus of attention in college students. Cognition and Emotion, 21(3), 558 -576.

Fenigstein & Vanable (1992) cited in Ellett,L. & Chadwick, P. (2007). Paranoid cognitions, failure, and focus of attention in college students. Cognition and Emotion, 21(3), 558 -576.

Forsell, Y., & Henderson, A. S. (1998). Epidemiology of paranoid symptoms in an elderly population. The British Journal of Psychiatry, 172(5), 429-432.

Fowler, D., & Morley, S. (1989). The cognitive-behavioural treatment of hallucinations and delusions: a preliminary study. Behavioural and Cognitive Psychotherapy, 17(3), 267-282.

Fowler, D., Garety, P., & Kuipers, E. (1995). Cognitive behaviour therapy for psychosis: Theory and practice. Sussex: John Wiley & Son.

Fowler, D., Hodgekins, J., Garety, P., Freeman, D., Kuipers, E., Dunn, G., … & Bebbington, P. E. (2012). Negative cognition, depressed mood, and paranoia: a longitudinal pathway analysis using structural equation modeling. Schizophrenia bulletin, 38(5), 1063-1073.

Freeman, D. (2006). Delusions in the non-clinical population. Current Psychiatry Reports, 8, 191-204.

Freeman, D. (2007). Suspicious minds: the psychology of persecutory delusions. Clinical psychology review, 27(4), 425-457.

Freeman, D., & Garety, P. (2014). Advances in understanding and treating persecutory delusions: a review. Social psychiatry and psychiatric epidemiology, 49(8), 1179-1189.

Freeman, D., & Garety, P. A. (2000). Comments on the content of persecutory delusions: Does the definition need clarification?. British Journal of Clinical Psychology, 39(4), 407-414.

Freeman, D., Dunn, G., Startup, H., Pugh, K., Cordwell, J., Mander, H., … & Kingdon, D. (2015). An explanatory randomised controlled trial testing the effects of cognitive behaviour therapy for worry on persecutory delusions in psychosis: the Worry Intervention Trial (WIT). The Lancet, 2(4), 305-313

Freeman, D., Emsley, R., Dunn, G., Fowler, D., Bebbington, P., Kuipers, E., … & Garety, P. (2014). The stress of the street for patients with persecutory delusions: a test of the symptomatic and psychological effects of going outside into a busy urban area. Schizophrenia bulletin, 41(4), 971-979.

Freeman, D., Evans, N., & Lister, R. (2012). Gut feelings, deliberative thought, and paranoid ideation: a study of experiential and rational reasoning. Psychiatry research, 197(1), 119-122.

Freeman, D., Garety, P. A., Bebbington, P. E., Smith, B., Rollinson, R., Fowler, D., … & Dunn, G. (2005). Psychological investigation of the structure of paranoia in a non-clinical population. The British Journal of Psychiatry, 186(5), 427-435.

Freeman, D., Garety, P. A., Fowler, D., Kuipers, E., Bebbington, P. E., & Dunn, G. (2004). Why do people with delusions fail to choose more realistic explanations for their experiences? An empirical investigation. Journal of consulting and clinical psychology, 72(4), 671-680.

Freeman, D., Garety, P. A., Kuipers, E., Fowler, D., & Bebbington, P. E. (2002). A cognitive model of persecutory delusions. British Journal of Clinical Psychology, 41(4), 331-347.

Freeman, D., Gittins, M., Pugh, K., Antley, A., Slater, M., & Dunn, G. (2008). What makes one person paranoid and another person anxious? The differential prediction of social anxiety and persecutory ideation in an experimental situation. Psychological medicine, 38(8), 1121-1132.

Freeman, D., Lister, R., & Evans, N. (2014). The use of intuitive and analytic reasoning styles by patients with persecutory delusions. Journal of behavior therapy and experimental psychiatry, 45(4), 454-458.

Freeman, D., McManus, S., Brugha, T., Meltzer, H., Jenkins, R., & Bebbington, P. (2011). Concomitants of paranoia in the general population. Psychological medicine, 41(5), 923-936.

Freeman, D., Pugh, K., Antley, A., Slater, M., Bebbington, P., Gittins, M., … & Garety, P. (2008). Virtual reality study of paranoid thinking in the general population. The British Journal of Psychiatry, 192(4), 258-263.

Freeman, D., Pugh, K., Vorontsova, N., Antley, A., & Slater, M. (2010). Testing the continuum of delusional beliefs: An experimental study using virtual reality. Journal of abnormal psychology, 119(1), 83.

Freeman, D., Slater, M., Bebbington, P. E., Garety, P. A., Kuipers, E., Fowler, D., … & Vinayagamoorthy, V. (2003). Can virtual reality be used to investigate persecutory ideation?. The Journal of nervous and mental disease, 191(8), 509-514.

Freeman, D., Stahl, D., McManus, S., Meltzer, H., Brugha, T., Wiles, N., & Bebbington, P. (2012). Insomnia, worry, anxiety and depression as predictors of the occurrence and persistence of paranoid thinking. Social psychiatry and psychiatric epidemiology, 47(8), 1195-1203.

Freeman, D., Waller, H., Harpur-Lewis, R. A., Moore, R., Garety, P., Bebbington, P., … & Jolley, S. (2015). Urbanicity, persecutory delusions, and clinical intervention: the development of a brief CBT module for helping patients with persecutory delusions enter social urban environments. Behavioural and cognitive psychotherapy, 43(1), 42-51.

Garety, P. A., & Freeman, D. (2013). The past and future of delusions research: from the inexplicable to the treatable. The British Journal of Psychiatry, 203(5), 327-333.

Garety, P. A., Freeman, D., Jolley, S., Dunn, G., Bebbington, P. E., Fowler, D. G., … & Dudley, R. (2005). Reasoning, emotions, and delusional conviction in psychosis. Journal of abnormal psychology, 114(3), 373.

Garety, P. A., Kuipers, E., Fowler, D., Freeman, D., & Bebbington, P. E. (2001). A cognitive model of the positive symptoms of psychosis. Psychological medicine, 31(2), 189-195.

Garety, P., Waller, H., Emsley, R., Jolley, S., Kuipers, E., Bebbington, P., … & Freeman, D. (2015). Cognitive mechanisms of change in delusions: an experimental investigation targeting reasoning to effect change in paranoia. Schizophrenia bulletin, 41(2), 400-410.

Gaudiano, B. A. (Ed.). (2015). Incorporating acceptance and mindfulness into the treatment of psychosis: Current trends and future directions. New York: Oxford University Press.

Gaudiano, B. A., & Herbert, J. D. (2006). Acute treatment of inpatients with psychotic symptoms using Acceptance and Commitment Therapy: Pilot results. Behaviour research and therapy, 44(3), 415-437.

Haddock, G., & Lewis, S. (2005). Psychological interventions in early psychosis. Schizophrenia Bulletin, 31(3), 697-704.

Haddock, G., & Spaulding, W. (2013). Family interventions for psychosis. Progress in Neurology and Psychiatry, 17(2), 18-19.

Hofmann, S. G., Sawyer, A. T., Witt, A. A., & Oh, D. (2010). The effect of mindfulness-based therapy on anxiety and depression: A meta-analytic review. Journal of consulting and clinical psychology, 78(2), 169.

Jaspers, K. (1963) General Psychopathology. In: Jones, H., Delespaul, P., & Van Os, J. (2003). Jaspers was right after all–delusions are distinct from normal beliefs. The British Journal of Psychiatry, 183(4), 285-286.

Johns, L. C., & Van Os, J. (2001). The continuity of psychotic experiences in the general population. Clinical psychology review, 21(8), 1125-1141.

Johns, L. C., Cannon, M., Singleton, N., Murray, R. M., Farrell, M., Brugha, T., … & Meltzer, H. (2004). Prevalence and correlates of self-reported psychotic symptoms in the British population. The British Journal of Psychiatry, 185(4), 298-305.

Kabat‐Zinn, J. (2003). Mindfulness‐based interventions in context: past, present, and future. Clinical psychology: Science and practice, 10(2), 144-156.

Kingston, J., & Ellett, L. (2014). Self-affirmation and nonclinical paranoia. Journal of behaviour therapy and experimental psychiatry, 45(4), 502-505.

Lau, M. A., Bishop, S. R., Segal, Z. V., Buis, T., Anderson, N. D., Carlson, L., … & Devins, G. (2006). The Toronto mindfulness scale: Development and validation. Journal of clinical psychology, 62(12), 1445-1467.

Laurens, K. R., Hobbs, M. J., Sunderland, M., Green, M. J., & Mould, G. L. (2012). Psychotic-like experiences in a community sample of 8000 children aged 9 to 11 years: an item response theory analysis. Psychological medicine, 42(7), 1495-1506.

Leff, J., Williams, G., Huckvale, M., Arbuthnot, M., & Leff, A. P. (2014). Avatar therapy for persecutory auditory hallucinations: what is it and how does it work?. Psychosis, 6(2), 166-176.

Linscott, R. J., & Van Os, J. (2013). An updated and conservative systematic review and meta-analysis of epidemiological evidence on psychotic experiences in children and adults: on the pathway from proneness to persistence to dimensional expression across mental disorders. Psychological medicine, 43(6), 1133-1149.

Longden, E., Corstens, D., Escher, S., & Romme, M. (2012). Voice hearing in a biographical context: a model for formulating the relationship between voices and life history. Psychosis, 4(3), 224-234.

Martinelli, C., Cavanagh, K., & Dudley, R. E. (2013). The impact of rumination on state paranoid ideation in a nonclinical sample. Behavior therapy, 44(3), 385-394.

McKie, A., Askew, K., & Dudley, R. (2017). An experimental investigation into the role of ruminative and mindful self-focus in non-clinical paranoia. Journal of behavior therapy and experimental psychiatry, 54, 170-177.

Melo, S. S., & Bentall, R. P. (2010). Coping in subclinical paranoia: A two nations study. Psychology and Psychotherapy: Theory, Research and Practice, 83(4), 407-420.

Menon, M., Balzanc, R. P., Harper-Romeo, K., Kumar, D., Andersen, D., Moritz, S., & Woodwarda, T. S. (2015). Psychosocial approaches in the treatment of psychosis: Cognitive behaviour therapy for psychosis (CBTp) and metacognitive training (MCT). Clinical schizophrenia & related psychoses, 1-24.

Morrison, A. P. (2001). The interpretation of intrusions in psychosis: an integrative cognitive approach to hallucinations and delusions. Behavioural and Cognitive Psychotherapy, 29(3), 257-276.

Morrison, A. P., Gumley, A. I., Schwannauer, M., Campbell, M., Gleeson, A., Griffin, E., & Gillan, K. (2005). The Beliefs about Paranoia Scale: preliminary validation of a metacognitive approach to conceptualizing paranoia. Behavioural and Cognitive Psychotherapy, 33(2), 153-164.

Morrison, A. P., Shryane, N., Fowler, D., Birchwood, M., Gumley, A. I., Taylor, H. E., … & Bentall, R. P. (2015). Negative cognition, affect, metacognition and dimensions of paranoia in people at ultra-high risk of psychosis: a multi-level modelling analysis. Psychological medicine, 45(12), 2675-2684.

Morrison, A. P., Wells, A., & Nothard, S. (2000). Cognitive factors in predisposition to auditory and visual hallucinations. British Journal of Clinical Psychology, 39(1), 67-78.

Morrison, A. P., Wells, A., & Nothard, S. (2002). Cognitive and emotional predictors of predisposition to hallucinations in non‐patients. British Journal of Clinical Psychology, 41(3), 259-270.

Morrison, A., Renton, J., Dunn, H., Williams, S., & Bentall, R. (2004). Cognitive therapy for psychosis: A formulation-based approach. Sussex: Routledge.

Mullen, R. (2003). Delusions: the continuum versus category debate. Australian and New Zealand Journal of Psychiatry, 37(5), 505-511.

Murphy, E. K., Tully, S., Pyle, M., Gumley, A. I., Kingdon, D., Schwannauer, M., … & Morrison, A. P. (2017). The Beliefs about Paranoia Scale: Confirmatory factor analysis and tests of a metacognitive model of paranoia in a clinical sample. Psychiatry research, 248, 87-94.

National Institute for Health and Care Excellence (NICE) (2014). Psychosis and Schizophrenia in adults: prevention and management. NICE Clinical Guideline CG178. [Online]. Available at: https://www.nice.org.uk/guidance/cg178 [Accessed: 03 January 2018].

Nuechterlein, K. H., Parasuraman, R., & Jiang, Q. (1983). Visual sustained attention: Image degradation produces rapid sensitivity decrement over time. Science, 220(4594), 327-329. DOI: 10.1126/science.6836276

O’Keeffe, J., Conway, R., & McGuire, B. (2017). A systematic review examining factors predicting favourable outcome in cognitive behavioural interventions for psychosis. Schizophrenia research, 183, 22-30.

Östling, S., & Skoog, I. (2002). Psychotic Symptoms and Paranoid Ideation in a Nondemented Population–Based Sample of the Very Old. Archives of General Psychiatry, 59(1), 53-59.

Peters, E. R., Joseph, S. A., & Garety, P. A. (1999). Measurement of delusional ideation in the normal population: introducing the PDI (Peters et al. Delusions Inventory). Schizophrenia bulletin, 25(3), 553.

Pharoah, F. M., Rathbone, J., Mari, J. J., & Streiner, D., (2003) Family intervention for schizophrenia. Cochrane Database of Systematic Reviews. 2003(4) DOI: 10.1002/14651858.CD000088

Poulton, R., Caspi, A., Moffitt, T. E., Cannon, M., Murray, R., & Harrington, H. (2000). Children’s self-reported psychotic symptoms and adult schizophreniform disorder: a 15-year longitudinal study. Archives of general psychiatry, 57(11), 1053-1058.

Scott, J., Chant, D., Andrews, G., & McGrath, J. (2006). Psychotic-like experiences in the general community: the correlates of CIDI psychosis screen items in an Australian sample. Psychological medicine, 36(2), 231-238.

Shawyer, F., Farhall, J., Thomas, N., Hayes, S. C., Gallop, R., Copolov, D., & Castle, D. J. (2017). Acceptance and commitment therapy for psychosis: randomised controlled trial. The British Journal of Psychiatry, 210(2), 140-148.

So, S. H., Freeman, D., Dunn, G., Kapur, S., Kuipers, E., Bebbington, P., … & Garety, P. A. (2012). Jumping to conclusions, a lack of belief flexibility and delusional conviction in psychosis: a longitudinal investigation of the structure, frequency, and relatedness of reasoning biases. Journal of abnormal psychology, 121(1), 129.

Steel, C. (2008). Cognitive behaviour therapy for psychosis: current evidence and future directions. Behavioural and Cognitive Psychotherapy, 36(6), 705-712.

Steel, C., Tarrier, N., Stahl, D., & Wykes, T. (2012). Cognitive behaviour therapy for psychosis: the impact of therapist training and supervision. Psychotherapy and psychosomatics, 81(3), 194-195.

Stefanis, N. C., Hanssen, M., Smirnis, N. K., Avramopoulos, D. A., Evdokimidis, I. K., Stefanis, C. N., … & Van Os, J. (2002). Evidence that three dimensions of psychosis have a distribution in the general population. Psychological medicine, 32(2), 347-358.

Strauss, J. S., (1969). Hallucinations and delusions as points on continua function: rating scale evidence. In: Van Os, J., Hanssen, M., Bijl, R. V., & Ravelli, A. (2000). Strauss (1969) revisited: a psychosis continuum in the general population?. Schizophrenia research, 45(1), 11-20.

Sugiura, Y. (2004). Detached mindfulness and worry: a meta-cognitive analysis. Personality and Individual Differences, 37(1), 169-179.

Tiernan, B., Tracey, R., & Shannon, C. (2014). Paranoia and self-concepts in psychosis: a systematic review of the literature. Psychiatry research, 216(3), 303-313.

Trower, P., Birchwood, M., Meaden, A., Byrne, S., Nelson, A., & Ross, K. (2004). Cognitive therapy for command hallucinations: randomised controlled trial. The British Journal of Psychiatry, 184(4), 312-320.

Tully, S., Wells, A., & Morrison, A. P. (2017). ‘You’ve got your own demons that you’ve got to fight every day’: A qualitative exploration of how people respond to the experience of psychosis. Psychology and Psychotherapy: Theory, Research and Practice.

Turkington, D., & McKenna, P. J. (2003). Is cognitive–behavioural therapy a worthwhile treatment for psychosis?. The British Journal of Psychiatry, 182(6), 477-479.

Turkington, D., Kingdon, D., & Weiden, P. J. (2006). Cognitive behavior therapy for schizophrenia. American Journal of Psychiatry, 163(3), 365-373.

Van der Gaag, M., Nieman, D., & Van den Berg, D. (2013). CBT for Those at Risk of a First Episode Psychosis: Evidence-based psychotherapy for people with an’At Risk Mental State’. Sussex: Routledge.

Van Os, J., & Verdoux, H. (2003). Diagnosis and classification of schizophrenia: Categories versus dimensions, distributions versus disease. In R. M. Murray, P. B. Jones, J. E.Susser, & M. van Os (Eds.), The epidemiology of schizophrenia (pp. 364−410). Cambridge: Cambridge University Press.

Verdoux, H., & van Os, J. (2002). Psychotic symptoms in non-clinical populations and the continuum of psychosis. Schizophrenia research, 54(1), 59-65.

Westbrook, D., Kennerley, H., & Kirk, J. (2007). An introduction to cognitive behaviour therapy: Skills and applications. London: Sage Publications.

Wigman, J. T., Vollebergh, W. A., Raaijmakers, Q. A., Iedema, J., Van Dorsselaer, S., Ormel, J., … & van Os, J. (2009). The structure of the extended psychosis phenotype in early adolescence—a cross-sample replication. Schizophrenia bulletin, 37(4), 850-860.

Wong, K. K., Freeman, D., & Hughes, C. (2014). Suspicious young minds: paranoia and mistrust in 8-to 14-year-olds in the UK and Hong Kong. British Journal of Psychiatry, 205(3) 221-229; DOI: 10.1192/bjp.bp.113.135467

Wood, L., Birtel, M., Alsawy, S., Pyle, M., & Morrison, A. (2014). Public perceptions of stigma towards people with schizophrenia, depression, and anxiety. Psychiatry Research, 220, 604-608.

Zimmermann, G., Favrod, J., Trieu, V. H., & Pomini, V. (2005). The effect of cognitive behavioral treatment on the positive symptoms of schizophrenia spectrum disorders: a meta-analysis. Schizophrenia research, 77(1), 1-9.