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insomnia and paranoia have been linked with negative affect. Sleepdifculties are a risk factor for developing emotional disorders suchas anxiety and depression (Ford and Kamerow, 1989; Breslau et al.,1996; Morphy et al., 2007), while negative affective states predictthe occurrence of paranoid thinking (see Freeman, 2007; Bentall

associated, and the associationwas partly explained by the presenceof anxiety and depression (Freeman et al., 2009). In a small group ofpatients with persecutory delusions (and a diagnosis of schizo-phrenia), moderate or severe insomnia was present in more than50%. This provides preliminary evidence of the potential importanceof insomnia for understanding paranoia. The central aim of thecurrent study is to corroborate this association by examining datafrom the British National Survey of Psychiatric Morbidity (2000)(Singleton et al., 2001a), a large population-based survey with

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Journal of Psychiatric Research 44 (2010) 1021e1026E-mail address: daniel.freeman@kcl.ac.uk (D. Freeman).1. Introduction

Difculties in falling or staying asleep are common. Approxi-mately 30% of the general population experience current symptomsof insomnia, with a third of this group having chronic insomnia(Ohayon, 2002;Walsh, 2004;Morin et al., 2006; Stewart et al., 2006).It is only in the last few years that it has been recognised thatparanoid thinking is almost as prevalent. At least 25% of the generalpublic regularly experience paranoid thoughts, and the lifetimeprevalence of persecutory delusions is approximately 5% (Freemanand Freeman, 2008; Rutten et al., 2008). Intriguingly, both

et al., 2008). Therefore insomnia exacerbates factors shown inseparate research to predict paranoia. It is plausible that sleepdifculties contribute to the occurrence of paranoia. An unfortunatedirect example of this can be seen in a treatment case series wheresleep deprivation for 36 h led to a worsening of delusions in indi-viduals with depressive psychosis (Benedetti et al., 1999).

Sleep difculties have been noted in people with schizophrenia,for example as a common prodromal symptom (Birchwood et al.,1989; Yung and McGorry, 1996), but only one study has directlyexamined insomnia and paranoia. In 300 individuals from thegeneral population, insomnia and paranoid ideation were stronglyReceived 23 September 2009Received in revised form24 March 2010Accepted 25 March 2010

Keywords:DelusionsParanoiaInsomniaAnxietyWorry0022-3956/$ e see front matter 2010 Elsevier Ltd.doi:10.1016/j.jpsychires.2010.03.018a b s t r a c t

It is clinically and theoretically plausible that insomnia contributes to the development and maintenanceof paranoid fears. The primary aim of the study was to establish in a large sample whether insomnia andparanoia are associated more strongly than by chance. Cross-sectional data on paranoia, insomnia,anxiety, worry, depression, irritability, and cannabis use were obtained from the second British NationalSurvey of Psychiatric Morbidity, a general population survey of adults aged 16e74 years living in GreatBritain (N 8580). It was found that insomnia was associated with an approximately two to threefoldincrease in paranoid thinking. Paranoia and insomnia were both strongly associated with the presence ofanxiety, worry, depression, irritability and cannabis use. In a path analysis the association of paranoia andinsomnia was partially explained by the affective symptoms, and, to a much lesser degree, cannabis use.The results are consistent with recent developments in the cognitive understanding of persecutorydelusions, in which insomnia, negative affect, and substance use are identied as key factors. Longitu-dinal studies of insomnia and paranoia, and tests of the effects of sleep interventions on levels ofparanoia, are now required to examine causality.

2010 Elsevier Ltd. All rights reserved.Persecutory ideation and insomnia: FinSurvey Of Psychiatric Morbidity

Daniel Freeman a,*, Traolach Brugha b, Howard MelPaul Bebbington e

aKings College London, Department of Psychology, PO Box 077, Institute of Psychiatry,bDepartment of Health Sciences, University of Leicester, UKcKings College London, Health Service and Population Research, Institute of PsychiatrydKings College London, Department of Biostatistics, Institute of Psychiatry, UKeDepartment of Mental Health Sciences, University College London, UK

journal homepage: www.eAll rights reserved.gs from the second British National

r b, Rachel Jenkins c, Daniel Stahl d,

mark Hill, London SE5 8AF, UK

le at ScienceDirect

iatric Research

vier.com/locate/psychires

iatrrandom sampling of communitymembers. The key prediction is thatinsomnia is associated with paranoia. A secondary prediction is thatthe association will be partly explained by levels of negative affectand associated experiences (anxiety, worry, depression, and irrita-bility). When attempting to account for the potential association it isrelevant to note that substance use has been separately linked tosleep difculties (e.g. Roth et al., 2006; Stein et al., 2008; Shibleyet al., 2008) and to delusions (e.g. Henquet et al., 2008; Morrisonet al., 2009; Johns et al., 2004); therefore a mediational role forcannabis use in an association of insomnia and paranoia is alsoscrutinised. However it is important to highlight that causal rela-tionships cannot be determined in this cross-sectional study.

2. Method

The second British National Survey of Psychiatric Morbidity wascarried out between March and September 2000. Adults aged16e74 years and living in private households in Great Britain weresampled. The data used in this study are based on interviewscarried out by experienced Ofce of National Statistics (ONS)interviewers. More details of the topics covered and the methodsused are given by Singleton et al., (2001a,b).

2.1. Participants

A stratied multi-stage random probability sample was used.There were two stages in the sample selection e the sampling of theprimary sampling units (PSUs), followed by the sampling ofaddresses within the selected PSUs. The PSUs were individual orgrouped postcode sectors. In the rst stage of sampling, the postcodesectors were stratied on the basis of a measure of socioeconomicstatus within a regional breakdown. First, postcode sectors weredivided into regions based on NHS Regional Ofce. All the PSUswithin each regional stratum were then further stratied on thebasis of the proportion of household heads in socioeconomic groups1e5 and 13, and sorted by the proportion of households withouta car based on 1991 census data. The postal sectors (the primarysampling units) were then sampled from each stratumwith a prob-ability proportional to size (i.e. the number of delivery points). In thisway a total of 438 postal sectors was selected. In the second stage ofthe sampling, 36 addresses were randomly selected within each ofthe selected postal sectors. This yielded a total sample of 15,804addresses. Interviewers visited these to identify private householdswith at least one person aged 16e74 years. One person was selectedfrom each qualifying household using the Kish (1965) grid method.Just under 70% of those approached agreed to a rst phase interview,which the vast majority completed in full (8580: 95%).

2.2. Assessments

The current study uses data from three survey instruments: theClinical Interview Schedule Revised (CIS-R e Lewis et al., 1992), thePsychosis Screening Questionnaire (PSQ; Bebbington and Nayani,1995), and the self-completion (screening) questionnaire versionof the Structured Clinical Interview for DSM-IV (SCID-II; First et al.,1997). The complete list of questions used in the survey is availableon the Internet (www.statistics.gov.uk/downloads/theme_health/PMA_2000_AppB.pdf).

Sleep problems were assessed using the CIS-R (Lewis et al.,1992). Insomnia was dened in three ways:

I1. Sleep difculties: problems in the past month with trying toget to sleep or with getting back to sleep (item D1).

I2. Insomnia of at least moderate severity: problems in the past

D. Freeman et al. / Journal of Psych1022month with trying to get to sleep or with getting back tosleep, occurring at least four nights in the past week, andtaking at least 1 h to attain sleep on an evening in the pastweek (items D1, D3, D5).

I3. Chronic insomnia: sleep problems for at least six months,problems with trying to get to sleep or with getting back tosleep, occurring at least four nights in the past week, taking atleast 1 h to attain sleep on an evening in the past week,together with reports of tiredness (items D1, D3, D5, D10, B1).

Persecutory ideation was also examined in three ways:

P1. Endorsement of the PSQ item In the past year, have there beentimes when you felt that people were deliberately acting toharm you or your interests?

P2. Endorsement of the PSQ item In the past year, have there beentimes you felt that a group of people was plotting to cause youserious harm or injury?

P3. Total paranoia score. A dimensionalmeasurewas constructed byselecting fteen paranoia-related items from the surveyassessments to approximate those of Freeman et al. (2005). Weused items 2, 3, 3a and 3b from the PSQ, relating to ideas ofpersecution, conspiracy and interference. From the SCID-II, weused items 2, 3, 4, 6, 10, 25, 26, 27, 28, 33 and 35 (e.g. Do youspend a lot of timewondering if you can trust your friends or thepeople you work with?, When you are out in public and seepeople talking, do you often feel that they are talking aboutyou?). The included items were chosen a priori, and progressedin content from mistrust through reference to persecution.

The occurrence of hallucinations was assessed by the PSQ item5, Over the past year, have there been times whenyou heard or sawthings that other people couldnt?

The presence of anxiety, worry, depression and irritability wereassessed using the CIS-R (Lewis et al., 1992). For the mediationanalysis, computed symptom count scores varying between 0 and 4were used (DVJ12, DVI11, DVG11, DVE11). A similar computedsymptom count (DVD11) was used for insomnia symptoms in thismediation analysis. The questions in the survey on drug use aretaken from the U.S. ECA study (Eaton and Kessler, 1985) and self-completed on a computer. In the current study the only drugvariable examined was cannabis use in the past year (No/Yes).

2.3. Analysis

The main analyses were carried out using the Stata 10.1 surveydata analysis commands, as these provide robust condence limitsfor the analysis of datasets of complex structure (StataCorp, 2008).Analyses were performed using data weighted to take account ofthe complex survey design (in particular, the fact only one personper household was sampled) and of non-response, in order toensure that the results were representative of the British householdpopulation aged 16e74 as a whole. Full details of the weightingprocedures are available online in the technical report (Singletonet al., 2001b). Logistic and linear regressions were used to testassociations of insomnia and paranoia.

The secondary analysis was an examination of the mediation ofthe relationship between insomnia and paranoia. A model withemotion and cannabis use as potential mediators was assessedusing a series of linear and logistic regression models (accountingfor the complex survey design). Mediation is a hypothesised causalchain in which an independent variable X affects a mediatingvariable Y, which in turn affects the outcome variable Z (Baron andKenny, 1986; MacKinnon, 2008). If the intervening mediator Yexplains the correlation between X and Z, we have a full media-

ic Research 44 (2010) 1021e1026tional model. If X still has an effect on Z after including themediator

Y in the model, the model is consistent with partialmediation. Themediation analysis was performed in four steps: i) a linearregression of paranoia scores on insomnia scores was used toestimate the total effect of insomnia ii) the proposed mediators,emotion and cannabis use, were added as independent variables inthe rst model iii) a linear regression of emotion on insomnia wascarried out and iv) a logistic regression of cannabis use on insomniawas performed, which enabled the indirect effects of insomnia onparanoia to be determined. Indirect paths were assessed using theSobel Aroian Test (MacKinnon et al., 2002). The Sobel tests wereproduced using a calculator and checked with an online softwareprogramme (http://people.ku.edu/wpreacher/sobel/sobel.htm).Because the cannabis use variable was dichotomous, the SobelAroian test for this indirect path was modied using the methoddescribed by MacKinnon and Dwyer (1993). The results are pre-sented in a path diagram with regression coefcients and 95%condence intervals. A single emotion variable was created for themediation analysis by performing a weighted principal axis factoranalysis using the four correlated variables depression, worry,anxiety and irritability. The factor analysis was carried out in SPSS

acting to harm you or your interests? was 809 (weighted 9.0%).

signicant sex differences in paranoia. Insomnia increased withage, while paranoia decreased with age. For instance, in theyoungest age group (16e25, n 907) 1.9% endorsed the paranoiaitem P2 and 9.2% reported insomnia (I2), whereas in the oldest agebracket (65e74, n 1268) 0.7% endorsed the paranoia item P2 and14.1% reported insomnia (all percentages weighted).

3.2. Association between insomnia and paranoia

There were strong associations between all the insomnia andparanoia variables (see Table 2). For instance, sleep difculties inthe past month were associated with 2.30 times the likelihood ofendorsing the item Have there been times when you felt thatpeople were deliberately acting to harm you or your interests?.Chronic insomnia increased almost vefold the likelihood ofendorsing the item Have there been times you felt that a group ofpeople was plotting to cause you serious harm or injury?. Theassociations became stronger as the severity of insomnia increased,and also as the severity of the content of the paranoid thoughts

cente)

D. Freeman et al. / Journal of Psychiatric Research 44 (2010) 1021e1026 1023Individuals endorsing the item Have there been times you felt thata group of peoplewas plotting to cause you serious harm or injury?numbered 146 (weighted 1.6%). The mean paranoia score was 2.48(SD 2.86, minimum 0, maximum 14). Information concerninginsomnia and paranoia by sex and age is presented in Table 1.Women had higher rates of insomnia, whereas there were few

Table 1Associations of insomnia and paranoia with sex and age.

Independent variable Dependent variable Parameter coding (weighted perpositively on dependent variabl

Sex P1 Male (8.8%)Female (9.4%)

P2 Male (1.7%)Female (1.3%)

P3 MaleFemale

I1 Male (35.0%)Female (44.0%)

I2 Male (10.8%)Female (14.2%)

I3 Male (6.0%)Female (8.0%)

Age P1 AgeP2 AgeP3 AgeI1 AgeI2 Age(2006) 15.0. It could not be performed using the complex surveydesign, but the scores derived from separate factor analyses withineach area correlated almost perfectly (r 0.99). The meditationalregression analyses were also repeated using the four emotionvariables individually as possible mediators to examine the size oftheir effects.

3. Results

3.1. Presence of insomnia and paranoia

Sleep difculties were present in 3380 participants (weighted38.0%), insomnia of at least moderate severity in 1120 participants(weighted 11.9%), and chronic insomnia in 623 participants(weighted 6.6%). The number of individuals endorsing the itemHave there been times when you felt that people were deliberatelyI3 Ageincreased. In linear regressions, the paranoia dimensional score(P3) was signicantly associated with sleep difculties, b 1.41, p