IQ and non-clinical psychotic symptoms in 12-year-olds: results from the ALSPAC birth cohort

Abstract

BackgroundNon-clinical psychotic symptoms appear common in children, but it is possible that a proportion of reported symptoms result from misinterpretation. There is a well-established association between pre-morbid low IQ score and schizophrenia. Psychosis-like symptoms in children may also be a risk factor for psychotic disorder but their relationship with IQ is unclear.AimsTo investigate the prevalence, nature and frequency of psychosis-like symptoms in 12-year-old children and study their relationship with IQ.MethodLongitudinal study using the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort. A total of 6455 children completed screening questions for 12 psychotic symptoms followed by a semi-structured clinical assessment. IQ was assessed at 8 years of age using the Wechsler Intelligence Scale for Children (3rd UK edition).ResultsThe 6-month period prevalence for one or more symptoms was 13.7% (95% CI 12.8–14.5). After adjustment for confounding variables, there was a non-linear association between IQ score and psychosis-like symptoms, such that only those with below average IQ score had an increased risk of reporting such symptoms.ConclusionsNon-clinical psychotic symptoms occur in a significant proportion of 12-year-olds. Symptoms are associated with low IQ and also less strongly with a high IQ score. The pattern of association with IQ differs from that observed in schizophrenia.

Prevalence of psychotic symptoms in childhood and adolescence: a systematic review and meta-analysis of population-based studies

“…A total of 19 studies met criteria for inclusion -5 interview studies (Horwood et al, 2008, Kelleher et al, 2008, Kelleher et al, In Press, Polanczyk et al, 2010, Poulton et al, 2000 and 14 self report questionnaire studies (Barragan et al, 2011, De Loore et al, 2011, Dhossche et al, 2002, Kelleher et al, In Press, Kinoshita et al, 2011, Lataster et al, 2006, Scott et al, 2009a, Scott et al, 2009b, Wigman et al, 2011, Yoshizumi et al, 2004, Yung et al, 2009) (see Table 1). …”

Peer Victimization in Childhood and Internalizing Problems in Adolescence: A Prospective Longitudinal Study

“…Child IQ was assessed using an abbreviated form of the Wechsler Intelligence Scale for Children-III (Wechsler et al 1992) during a clinic assessment at 8 years (see Horwood et al 2008).…”

Why we need more debate on whether psychotic symptoms lie on a continuum with normality

“…First, it soon becomes evident after only a cursory perusal of the literature that even workers motivated by the idea of a continuum find it impossible to resist setting a threshold above which a hallucination or delusion may be defined. Hence, the phenomena are described as possible or probable or definite, or a distinction is made between items endorsed from a questionnaire and those elicited by lay interviewers or through clinical interview and subsequently verified (Laurens et al 2007 ;Horwood et al 2008). This methodology seems perfectly apt.…”

“…Another methodological issue concerns the nature of the questions and the expectations they engender in participants. The Dunedin questionnaire has served as a template for many similar studies (Poulton et al 2000 ;Horwood et al 2008), and used the schizophrenia section of the Diagnostic Interview Schedule for Children to elicit phenomena. Questions begin with a preamble such as : ' Some people believe in mind reading or being psychic.…”