Genetic and environmental influences on the stability of psychotic experiences and negative symptoms in adolescence

Background: Psychotic experiences (PEs) such as paranoia and hallucinations, and negative\ud symptoms (NS) such as anhedonia and flat affect, are common in adolescence. PENS\ud increase risk for later psychiatric outcomes, particularly when they persist. The extent to\ud which genetic and environmental influences contribute to the stability of PENS in mid to late\ud adolescence is unknown. Methods: Using the Specific Psychotic Experiences Questionnaire\ud (SPEQ) twice across ~9 months in adolescence, N = 1,448 twin pairs (M = 16.32 (0.68))\ud reported experiences of paranoia, hallucinations, cognitive disorganisation, grandiosity, and\ud anhedonia, and their parents reported on a range of NS. Individuals were split into lowscoring, decreasing, increasing, and persistent groups for each subscale. Frequencies and\ud mean differences in distress, depression traits, and emotional problems were investigated\ud across groups. Longitudinal structural equation modelling was used to estimate the\ud etiological components underlying the stability of PENS. Results: Phenotypic stability was\ud moderate for all PENS (\ud r = .59-.69). Persistent PENS across 9 months were associated with\ud greater levels of distress (V = 0.15-0.46, for PEs only), depression traits (\ud d = 0.47-1.67,\ud except grandiosity), and emotional problems (\ud d = 0.47-1.47, except grandiosity and\ud anhedonia) at baseline compared to groups with transitory or low levels of PENS. At both\ud ages PENS were heritable and influenced by shared and nonshared environment. Genetic\ud influences contributed 38%-62%, and shared environment contributed 13%-33% to the\ud stability of PENS. Nonshared environment contributed 34%-41% (12% for parent-rated NS).\ud There was strong overlap of genetic and shared environmental influences across time, and\ud lower overlap for nonshared environment. Imperfect stability of PENS was at least partly due to\ud non-shared environmental influences. Conclusions: When adolescent PENS persist over time,\ud they are often characterised by more distress, and higher levels of other psychopathology.\ud Both genetic and environmental effects influence stability of PENS