Formal thought disorder: Self-report in non-clinical populations

This study present data from 300 unselected individuals who had completed the Formal Thought Disorder-Self Scale (FTD-S) (Study 1) and from a separate sample of over 150 unselected individuals who had completed the FTD-S and also had a relative or friend complete the Formal Thought Disorder-Other Scale (FTD-O) (Study 2). The questionnaire, originally devised to measure self-ratings of thought disorder in clinical samples, was adapted from a yes-no questionnaire to a 4 point Likert format, to more sensitively determine the extent to which such characteristics may be reported amongst the healthy population. Principal Components Analysis of the FTD-S scale suggested a three-component solution for which we proposed the nomenclature of: odd speech, conversational ability and working memory deficit. Study 2 found that the FTD-S (self-report) and the FTD-O (other rated) reached a significant but low correlation (r= .29; p <0.01); these findings are discussed in terms of its significance for self-report of Formal Thought Disorder and proneness to psychosis.