Mollon J, et al. - The researchers aimed to delineate the course of general and specific cognitive functions in individuals with psychotic disorders, psychotic experiences, and depression. As per findings, dynamic developmental processes were observed to be involved in the origins of psychotic disorder. These affected both verbal and nonverbal abilities throughout the first 2 decades of life and leading to increasing dysfunction. In other psychiatric disorders (such as psychosis with depression and depression), these developmental processes did not show manifestation.

Methods

• Researchers performed a prospective cohort study [the Avon Longitudinal Study of Parents and Children (ALSPAC)] comprising all live births between April 1, 1991, and December 31, 1992, in Avon, England.
• From September 2015 to July 2016, analysis was performed.
• They included participants who underwent cognitive testing at ages 18 months and 4, 8, 15, and 20 years and psychiatric assessment at age 18 years.
• They performed comparison of individuals with psychotic disorder, psychosis with depression, psychotic experiences, and depression with controls.
• For this study, outcomes included full-scale, verbal, and nonverbal IQ at ages 18 months and 4, 8, 15, and 20 years, as well as measures of processing speed, working memory, language, visuospatial ability, and attention at ages 8 and 20 years.

Results

• In this longitudinal birth cohort study, the following numbers of individuals were available for analyses: 511 (238 male [46.6%]) at age 18 months (mean [SD] age, 1.53 [0.03] years), 483 (229 male [47.4%]) at age 4 years (mean [SD] age, 4.07 [0.03] years), 3,930 (1,679 male [42.7%]) at age 8 years (mean [SD] age, 8.65 [0.29] years), 3,783 (1,686 male [44.6%]) at age 15 years (mean [SD] age, 15.45 [0.27] years), and 257 (90 male [35.0%]) at age 20 years (mean [SD] age, 20.06 [0.55] years).
• Continually increasing deficits were noticed among individuals with psychotic disorder between infancy (18 months) and adulthood (20 years) in full-scale IQ (effect size of change [ESΔ]=-1.09, P=.02) and nonverbal IQ (ESΔ=-0.94, P=.008).
• A small, increasing deficit was observed in the depression group between infancy and adulthood in nonverbal IQ (ESΔ = -0.29, P=.04).
• The psychotic disorder group showed developmental lags (ie, slower growth), between ages 8 and 20 years, in measures of processing speed (ESΔ = -0.68, P=.001), working memory (ESΔ = -0.59, P=.004), and attention (ESΔ = -0.44, P=.001) and large, static deficits in measures of language (ES = -0.87, P=.005) and visuospatial ability (ES = -0.90, P=.001).
• Researchers identified only weak evidence for cognitive deficits in the psychosis with depression group and the psychotic experiences group.