Altered syntactic abilities in first episode patients: An inner phenomenon characterizing psychosis

Background: Research has consistently shown that language abilities represent a core dimension of psychosis; however, to date, very little is known about syntactic comprehension performance in the early stages of psychosis. This study aims to compare the linguistic abilities involved in syntactic comprehension in a large group of First Episode Psychosis (FEP) patients and healthy controls (HCs). Methods: A multiple choice test of comprehension of syntax was administered to 218 FEP patients (166 non-affective FEP patients [FEP-NA] and 52 affective FEP patients [FEP-A]) and 106 HCs. All participants were asked to match a sentence they listen with one out of four vignettes on a pc screen. Only one vignette represents the stimulus target, while the others are grammatical or non-grammatical (visual) distractors. Both grammatical and non-grammatical errors and performance in different syntactic constructions were considered. Results: FEP committed greater number of errors in the majority of TCGB language domains compared to HCs. Moreover, FEP-NA patients committed significantly more non-grammatical (z = 3.2, p = 0.007), locative (z = 4.7, p < 0.001), passive-negative (z = 3.2, p = 0.02), and relative (z = 4.6, p < 0.001) errors compared to HCs as well as more passive-affirmative errors compared to both HCs (z = 4.3, p < 0.001) and FEP-A (z = 3.1, p = 0.04). Finally, we also found that both FEP-NA and FEP-A committed more grammatical (FEP-NA: z = 9.2, p < 0.001 and FEP-A: z = 4.4, p < 0.001), total (FEP-NA: z = 8.2, p < 0.001 and FEP-A: z = 3.9, p = 0.002), and active-negative (FEP-NA: z = 5.8, p < 0.001 and FEP-A: z = 3.5, p = 0.01) errors compared to HCs. Conclusions: This study shows that the access to syntactic structures is already impaired in FEP patients, especially in those with FEP-NA, ultimately suggesting that language impairments represent a core and inner feature of psychosis even at early stages.