Formal Thought Disorder: Self-report in Non-clinical Populations

Formal thought disorder (FTD), a range of language and cognitive deficits clinically characterized by loose associations and incoherent speech (Andreasen, 1979), can be found in people with schizophrenia and other psychoses [Lott, Guggenbuhl, Schneeberger, Pulver, & Stassen, 2002), some personality and severe anxiety disorders (Gandolfo, Templer, Cappeletty, & Cannon, 1991; Lee, Zoung-Soul, Kwon, & 2005), developmental disorders (Dykens, Volkmar, & Glick, 1991; Caplan, Guthrie, Tang, Nuechterlein, & Asarnow, 2011), and crucially, at subclinical levels in a minority of nonclinical individuals (Barrera, 2006). Its proposed cognitive correlates include executive [Kerns & Berenbaum, 2002; Barrera, McKenna, & Berrios, 2005; Stirling, Hellewell, Blakey, & Deakin, 2006; Dibben, Rice, Laws, & McKenna, 2009), semantic (Melinder & Barch, 2003; Doughty & Done, 2009), and working memory deficits (Kiefer, Martens, Weisbrod, Hermle, & Spitzer, 2009; Barch & Berenbaum, 1997; Berenbaum, Kerns, Vernon, & Gomez, 2008). Subclinical FTD is a consistent finding in relatives of schizophrenia patients and occurs at an incidence greater than that of schizophrenia itself (Gambini, Campana, Macciardi, & Scarone, 1997; Levy, Coleman, Sung, Ji, Matthysse, Mendell, & Titone, 2010; Kiang, 2010; Bove, 2008). Symptoms of FTD can be observed in children considered to be at risk of schizophrenia (Ott, Roberts, Rock, Allen, & Erlenmeyer-Kimling, 2002). Relatives of schizophrenia, mania, and schizo-affective patients show FTD that mirrors, with lower severity, that of their affected relatives (Soloway, Holzman, Coleman, Gale, & Shenton, 1989). There is an association between being related to someone with schizophrenia and manifesting (subclinical) formal thought disorder (Romney, 1990). Such findings testify to the importance of assessing these characteristics in the non-clinical population. An instrument focused on assessing FTD would also complement other selfreport scales for various psychosis-prone experiences in healthy individuals, including delusions and hallucinations (Peters, Joseph, & Garety, 1999; Launey & Slade, 1982). Within the literature focused on schizotypal personality, the Schizotypal Personality Questionnaire (SPQ) (Raine, 1991), modelled on DSM-III-R criteria, contains one subscale that assesses vague and confused speech but without gross incoherence. Although this 'odd speech' scale ascertains attenuated features of FTD in people with schizotypal personality, it does not cover classical symptoms of FTD (e.g. clanging, neologisms) or the non-verbal and paralinguistic characteristics of the heterogeneous presentation of formal thought disorder.Several instruments have been developed to assess FTD including the Thought, Language and Communication Scale (TLC) (Andreasen, 1979), the Thought and Language Index (TLI) (Liddle, Ngan, Caissie, Anderson, Bates, Quested, White, & Weg, 2002), and the Thought Disorder Index (TDI) (Johnston & Holzman, 1979). More recently, the Formal Thought Disorder-Self scale was developed for the self-assessment by patients, along with an observer based questionnaire completed by someone who knows the subject ('FTD-O: observer') (Barrera, McKenna, & Berrios, 2008). Since both FTD scales assess classical symptoms of FTD along with pragmatics, paralinguistic, nonverbal, and cognitive aspects of speech they seem to provide a comprehensive and detailed assessment of communication disturbances seen among people with severe mental illness. We suggest that these instruments would help research into the different components of FTD as well as would allow the screening of populations for subjects with higher levels of thought disorder.An issue often debated is whether patients with clinical levels of thought disorder lack insight into their communication difficulties; the few empirical studies available actually reveal a degree of awareness of FTD in those with thought disorder (McGrath, Allman 2000; Barrera, McKenna, & Berrios, 2009). …