Objective: To examine childhood ADHD symptoms in regard to their association with a number of illness-related variables including risk factors, early neurodevelopment, premorbid functioning and clinical characteristics in patients with schizophrenia-spectrum psychoses.
Methods: One-hundred and twenty-two first-episode patients with DSM-IV schizophrenia-spectrum disorders were retrospectively assessed by means of their biological mothers for childhood ADHD symptoms. Using correlational analyses and hierarchical regression models, the severity of ADHD symptoms was examined in relation to familial liability to schizophrenia, obstetric complications, milestones attainment delay, premorbid functioning during childhood and adolescence, age at illness onset, episode psychopathology and response to treatment after one-month trial with antipsychotic medication.
Results: Twenty-one patients (17%) met DSM-IV criteria for childhood ADHD. Univariate analyses showed that severity of childhood ADHD symptoms was related to male gender, obstetric complications, delayed milestones attainment, poor school functioning and an earlier age of onset of psychotic symptoms. Hierarchical regression analyses showed that severity of childhood ADHD symptoms was independently predicted by obstetric complications and neurodevelopmental delay, with no further variables entering in the regression models. Path analyses showed that obstetric complications had both direct and indirect effects, through neurodevelopmental delay, on ADHD symptoms.
Conclusions: These findings are consistent with a neurodevelopmental model of schizophrenia and with the hypothesis of shared environmental risk factors between ADHD and schizophrenia-spectrum disorders. Childhood ADHD symptoms in schizophrenia-spectrum disorders appear to be an epiphenomenon of obstetric complications and early neurodevelopment delay with no further influence on the clinical expression of the illness.
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