Diagnostic criteria for ADHD require symptoms of inattention and hyperactivity/impulsivity that persist over time and are present to some degree in at least two contexts (e.g., in school and at home), causing substantial impairments. However, the degree to which symptoms are present across situations varies from individual to individual. At one end of the spectrum, individuals may show severe symptoms in several contexts (i.e., pervasive ADHD) while others show severe symptoms only in one context (i.e., situational ADHD). What underpins the pervasive and situational manifestations is not well understood, and the impact of context-related dysfunction on concurrent impairment and future outcome needs further investigation.

The purpose of the present study are:

1. To test for the existence of distinctive classes of pervasive and situational ADHD in cross-sectional population level data (using data from the ALSPAC-study).
2. To compare pervasive vs. situational ADHD classes in terms of: i) Sex, emotion processing, cognitive functioning (i.e., different aspects of attention and IQ), and aspects of the family environment ii) Comorbidity (pro-social behaviour, emotional symptoms, conduct problems, and peer-problems) iii) Long-term consequences (mental health, substance abuse, education/employment, and physical health)